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new characteristic periods of the magnetic sunspot area time-series have been found in two atmospheric time-series variables: neutron counts and atmospheric electric potential gradient. the data considered comprises two solar cycles (21, 22) and spans from 1978 to 1990. using a non-linear approach this study reveals the existence of similar and correlated features in sunspot areas as well as neutron counts and atmospheric electric potential gradient, favouring the possibility that the sun's activity affects the earth's atmosphere and weather at a time-scale between 150 to 300 days. moreover, we found five characteristic periods in the sunspot area time-series, four of which are detected in the neutron counts, and three in the atmospheric electric field. these values are consistent with the periods predicted for stationary rossby waves existing inside the sun. surprisingly, this reveals that instabilities on the solar magnetic field caused by rossby waves in the sun's interior are indirectly affecting the activity of the heliosphere, the earth's atmosphere and weather. | rieger-type periodicities on the sun and the earth during solar cycles 21 and 22 |
two of the most useful properties of individual filaments are not adequately understood. these are chirality and lifetime. the goal in this study is to analyze chirality and lifetime of filament and filament channels over a period of 2 years during the rise of current solar cycle 24 from may 2010 to may 2012. here we report on the results of cataloging for the initial months. systematic documentation of filament chirality will greatly help in forecasting the related helicity of cmes and their interaction with the magnetic field of earth. better knowledge of filament lifetime is needed to anticipate their eruption along with the occurrence of cmes. we are documenting lifetimes of filaments because their durations are much shorter than previously reported. by studying their lifetimes we gain a better understanding of the close relationship between filament evolution and cme buildup because they evolve and erupt hand-in-hand. we have determined the chirality of filaments using direct and indirect methods. the direct method is based on the slant of filament barbs observed in hα. the main indirect method employs the chirality of filament channels as seen in coronal cells in 193 å images. another indirect method is based on the skew of flare loops and coronal loops. by comparing these different techniques we are able to learn which method or combination of methods is most effective. we find very few exceptions to the hemispheric pattern of dextral filaments in the northern hemisphere and sinistral filaments in the southern hemisphere. the exceptions to the hemispheric pattern is primarily due to differential rotation acting on active regions whose relative locations are more north-south than east-west of each other. most exceptions are recognizable at the time filaments develop. we confirm the overall orientation of cme flux ropes in space can be anticipated from their associated filaments. | the chirality and lifetime of filaments and filament channels |
the most regular of all daily geomagnetic field variations is the so-called solar quiet, or sq, variation. it is attributed to the two current vortices flowing in the e-region of the dayside ionosphere. we present an investigation of the time-dependent parameters of sq variation for the historical minimum of solar activity in 2008. we apply "measure of anomalousness" algorithm to detection of magnetically quiet days. the global maps of seasonal sq amplitudes of the three orthogonal components are derived using 75 intermagnet and 46 supermag stations at low and middle latitudes. the global sq amplitudes are compared to the previous coupled magnetosphere-ionosphere-thermosphere (cmit) model simulations and show good agreement. significant variability was found in sq(x) and sq(y) based on the solar activity and latitude, while almost no difference is observed in sq(z) for across all latitudes and seasons. we analyze equivalent sq current system using observatory data from the australian mainland and narrow european-african latitudinal segment. sq current system also strongly depends on solar activity, as current vortices are strongest in the local summer-hemisphere and disintegrate during local winter. the dynamics of sq variation along the solar cycles 23 and 24 is also discussed and compared to swarm-based spherical harmonic sq model. | solar quiet daily (sq) geomagnetic variation during minimum of solar cycle 23/24 |
the strength of the sun's dipole moment at solar minimum is long known to be a good precursor for the forecasting of the amplitude of the following solar activity cycle. the buildup of the polar fields through the photospheric dispersal of magnetic flux liberated by the decay of active regions is now being modelled very accurately using a variety of surface flux transport models. less clear is the role played by the polar fields in the dynamo loop. i some classes of dynamo models it is crucial, while in others it is a mere side-effect of the dynamo operating in the interior. in this presentation i will use a variety of current solar dynamo models to illustrate this diversity of roles played by the polar fields. i will also argue that at this point, the primary uncertainties lie not with the buildup of the polar fields, but rather with its submergence into the solar interior, the essential prerequisite for participating in the dynamo loop. clarifying this key issue observationally requires an accurate accounting of magnetic flux balance for the polar caps (transport, emergence, submergence and in situ production) for which out-of-the-ecliptic observations are likely essential. | the sun's polar magnetic field as a key constraint on dynamo models of the solar cycle |
we compare the dating scales of natural and annalistic archives on the basis of historical data about sunspots seen with the unaided eye and auroras at low and middle latitudes, on the one hand, and radionuclide data from natural archives, on the other hand. our conclusion is the following: for the common era, there is no need to doubt the correctness of the historical scale established by scaliger. we also note that the consideration of long-term changes in solar activity with the use of different independent proxies may help in determining the reliability of radionuclide reconstructions and the long-period cycles of magnetic activity revealed from them. | principle of witnesses and the solar activity chronology |
we employ a time-distance measurement procedure, similar to the one used by ilonidis et al in their 2013 work, to detect solar subsurface structures associated with emerging magnetic flux. we compute the spatially-averaged cross-covariance of dopplergram signals, and fit to a gabor wavelet so that the phase travel time of acoustic waves can be extracted. deviations from the mean phase travel time are interpreted as fluctuations in density and gas pressure. we independently confirm the analysis of ar10488 from stathis et al (2013), a result that was hotly debated after publishing. we also calibrate this time-distance method using numerical models provided by hartlep et al (2011) and stejko et al (under review). based on this calibration, we propose an estimate for the magnitude of local sound-speed perturbations necessary to produce the observed signal. | early detection of emerging magnetic flux using time-distance helioseismology |
helioseismic programs from the ecliptic plane have enabled us to map solar flows for a large part of the sun. the solar poles, however, remain largely unexplored. flux-transport dynamo models rely on meridional flows transporting magnetic flux to the polar regions, however, high-latitude flows remain a mystery. we use data from the helioseismic and magnetic imager (hmi) to demonstrate the limits of what can be done from the ecliptic plane, and how that limits our knowledge of the high-latitude sun. | flows in the polar regions of the sun: limits of observing from the ecliptic |
space radiation is one of the most important risks to astronauts on space missions, especially on a future planetary mission to mars which would last at least 2-3 years. the radiation assessment detector (rad) on nasa's mars science laboratory (msl) was designed to detect and analyze the most biologically hazardous energetic particle radiation on the martian surface, as part of the msl's curiosity rover landed on mars on august 6, 2012. since then, rad has been providing the first-ever measurements of the cosmic ray induced energetic particle radiation environment on the martian surface for about 8 earth years. rad measurements quantify the radiation hazard to humans on a mars mission. we analyze the omnipresent galactic cosmic rays (gcr) radiation field recorded by rad from the beginning of the measurements on august 6, 2012 until the end of solar cycle 24. we observe that the martian surface radiation increased by about 50% due to the declining solar activity and the ensuing changes in the global heliospheric magnetic field configuration. we quantify the temporal evolution of the measured dose rate as a function of sunspot numbers and find a delay between indicators for solar activity and dose rate from gcrs. this quantification can be used to provide empirical forecasts of the martian gcr surface radiation level by about 6 months suggested by the existing rad data, or even up to about one year during odd solar cycles, as suggested by measurements of the long-term gcr evolution near earth. however, a better understanding of the solar-cycle dependence of the delay time needs further continuous long-term rad observations on mars. | empirical forecast of the gcr-induced radiation environment on mars |
in a polytropic process, the plasma transits from one state to another under constant specific heat. during a polytropic transition, the plasma density and temperature are related through the polytropic index which characterizes specific plasma streamlines. recent studies have shown that in the presence of potential energy, the polytropic index is related with the kappa distributions. the exact relationship involves the polytropic index, the kappa index (the parameter that governs and labels the kappa distributions), and the potential degrees of freedom (spatial average of the potential energy normalized by the kinetic energy). the determination of this relationship helps to understand the nature and characteristics of the potential energy acting on the plasma particles. in this study, we derive the polytropic and the kappa indices of the solar wind plasma, by analyzing wind in-situ observations at ~ 1 au, over the last two solar cycles. we determine the relationship between the polytropic and kappa indices in an annual basis and derive the potential degrees of freedom. the potential degrees of freedom exhibit negative correlations with the solar activity and the interplanetary magnetic field. our results indicate the possible function and geometry of the interplanetary potential and its correlation with the solar activity. | long term correlations between polytropic indices and kappa distributions in solar wind protons at 1 au |
in this paper we explore the millennial oscillations (or hallstatt cycle) of the baseline solar magnetic field, total solar irradiance and baseline terrestrial temperature detected from principal component analysis of the observed solar background magnetic field. we confirm the existence of these oscillations with a period of 2100-2200 years with the similar oscillations detected in carbon 14c isotope abundances and with wavelet analysis of solar irradiance in the past 12 millennia indicating the presence of this millennial period among a few others. we also test again the idea expressed in our paper zharkova et al, 2019 that solar inertial motion (sim) can cause these millennial variations because of a change of the distance between the sun and earth. in this paper we use the s-e distance derived from the current jpl ephemeris, finding that currently starting from the maunder minimum the sun-earth distance is reducing by 0.00025 au per 100 years, or by 0.0025 au per 1000 years.. we present the estimation of variations of solar irradiance caused by this variation of the s-e distance caused by solar inertial motion (sim) demonstrating these variations to be closely comparable with the observed variations of the solar irradiance measured by the satire payload. we also estimate the baseline temperature variations since maunder minimum caused by the increase of solar irradiance caused by the recovery from grand solar minimum and by reduction of the s-e distance caused by sim. these estimations show that the sun will still continue moving towards the earth in the next 700 years that will result in the increase of the baseline terrestrial temperature by up to 2.5°c in 2700. these variations of solar irradiance will be over-imposed by the variations of solar activity of 11 cycles and the two grand solar minima occurring in 2020-2053 and 2370-2415 caused by the double dynamo actions inside the sun. | millennial solar irradiance forcing (hallstatt's cycle) in the terrestrial temperature variations |
a classification of solar wind streams according to the main hydrodynamic parameters -- a combination of the velocity (fast or slow), temperature (hot or cold) and density (dense or rarefied) of protons -- is considered. according to this approach, we specify eight types of the solar wind: fast-hot-dense (fhd), fast-hot-rarefied (fhr), fast-cold-dense (fcd), etc. as an additional parameter, the proton plasma b is taken into account for description of the magnetic state of solar wind streams (high-, mid-, low-magnetized subtypes). the listed types of streams occur with different frequencies depending on the phases of solar activity cycles. this classification is compared with the classical division of solar wind streams into high-speed streams (hsss) from coronal holes, coronal mass ejections (cmes) and slow solar wind from the streamer belt. the comparison is carried out for the events in august 2010 and may 2011 when cme–cme and cme–hss interactions, respectively, were observed. in both cases there was the rare fcd-type of the wind. we concluded that the classical description of the large-scale structure of solar wind (hours and days), in particular, consideration of the solar wind ion composition, makes it possible to determine the nature and source of solar wind streams, whereas consideration of the hydrodynamic parameters including b is useful for a detailed description of the small-scale structure (minutes) of complex regions appeared in the cases of interaction of several streams in the heliosphere. | large-scale and small-scale structure of interacting solar wind streams |
solar cycle 24 is the weakest cycle in modern era of space- and ground-based observations. the number of sunspots visible on solar disk and other measures of magnetic activity have significantly decreased from the last cycle. it was also preceeded by an extended phase of low activity, a period that raised questions on our understanding of the solar activity cycle and its origin. this unusual behavior was not only limited to the visible features in sun's atmosphere, the helioseismic observations also revealed peculiar behavior in the interior. it was suggested that the changes in magnetic activity were confined to shallower layers only, as a result low-degree mode frequencies were found to be anti-correlated with solar activity. here we present results on the progression of cycle 24 by analyzing the uninterrupted helioseismic data from gong and sdo/hmi, and discuss differences and similarity between cycles 23 and 24 in relation to the solar activity. | solar activity in cycle 24 - what do acoustic oscillations tell us? |
the axial dipole moments of emerging active regions control the evolution of the axial dipole moment of the whole photospheric magnetic field and the strength of polar fields. hale's and joy's laws of polarity and tilt orientation affect the sign of the axial dipole moment of an active region, determining the normal sign for each solar cycle. if both laws are valid (or both violated), the sign of the axial moment is normal. however, for some active regions, only one of the two laws is violated, and the signs of these axial dipole moments are the opposite of normal. the opposite-sign axial dipole moments can potentially have a significant effect on the evolution of the photospheric magnetic field, including the polar fields.we determine the axial dipole moments of active regions identified from magnetographic observations and study how the axial dipole moments of normal and opposite signs are distributed in time and latitude in solar cycles 21-24.we use active regions identified from the synoptic maps of the photospheric magnetic field measured at the national solar observatory (nso) kitt peak (kp) observatory, the synoptic optical long term investigations of the sun (solis) vector spectromagnetograph (vsm), and the helioseismic and magnetic imager (hmi) aboard the solar dynamics observatory (sdo).we find that, typically, some 30% of active regions have opposite-sign axial dipole moments in every cycle, often making more than 20% of the total axial dipole moment. most opposite-signed moments are small, but occasional large moments, which can affect the evolution of polar fields on their own, are observed. active regions with such a large opposite-sign moment may include only a moderate amount of total magnetic flux. we find that in cycles 21-23 the northern hemisphere activates first and shows emergence of magnetic flux over a wider latitude range, while the southern hemisphere activates later, and emergence is concentrated to lower latitudes. we also note that cycle 24 differs from cycles 21-23 in many ways. cycle 24 is the only cycle where the northern butterfly wing includes more active regions than the southern wing, and where axial dipole moment of normal sign emerges on average later than opposite-signed axial dipole moment. the total axial dipole moment and even the average axial moment of active regions is smaller in cycle 24 than in previous cycles. | axial dipole moments of solar active regions in cycles 21-24 |
several studies have noted on changes in the properties of sunspots, and in the mutual relations between various global parameters of solar magnetic activity (e.g. uv/euv irradiance, radio and ir emissions, tsi/ssi), as well as between solar and ionospheric parameters since the onset of solar cycle 23. these changes have been suggested to be related to the overall reduction of solar activity at the aftermath of the decline of the grand modern maximum of solar activity that prevailed during most of the 20th century. we have recently derived the longest record of coronal magnetic field intensities since 1968 using mount wilson observatory and wilcox solar observatory observations of the photospheric magnetic field and the pfss model, and compared it with the heliospheric magnetic field observed at the earth. we found that the time evolution of the coronal magnetic field during the last 50 years agrees with the heliospheric magnetic field only if the effective coronal size, the distance of the coronal source surface of the heliospheric magnetic field, is allowed to change in time. we calculated the optimum distance for each solar rotation and found that it experienced an abrupt decrease in the late 1990s. the effective volume of the solar corona shrunk to less than one half of its previous value during a short period of only a few years. this shrinking was related with a systematic change in the structure of the coronal magnetic field during the same time interval. we review these dramatic changes in the solar corona and discuss their possible connection to the changes in the different solar activity parameters and the reduction of the overall solar activity. | abrupt shrinking of solar corona in late 1990s and related changes in solar magnetic structure |
in the inner region of saturn's rotationally-dominated magnetosphere, the governing magnetic field contributors are the internal magnetic field and the magnetodisc current sheet. the equatorially confined plasma sourced predominantly by the moon enceladus stretches saturn's magnetic field lines into the characteristic 'magnetodisc' geometry. the extent of this effect varies due to both external and internal dynamical processes that perturb the system.in this study, we use the complete dataset collected by the cassini spacecraft to determine whether the magnetosphere is compressed, stretched or near some prescribed ground state. we find that there is an underlying dawn-dusk asymmetry in the ground state of saturn's magnetosphere, where the field is more compressed at dusk compared to dawn. whilst saturn spent a significant period of the cassini mission near its ground state, we find evidence for large-scale stresses acting on the system, including large compression events that coincide with the declining phase of the solar cycle. these results are then compared to propagated solar wind data. in addition, approximately two thirds of our dataset is well described by the internal field and current sheet models, signifying the system was in steady-state during these passes. we further discuss the drivers for the non-steady state periods at saturn and what this implies for the global dynamics of saturn's magnetosphere. | finding the drivers for a non-steady state and large-scale stresses acting on the saturnian magnetosphere |
we study the variation of subsurface flows in the presence of magnetic activity during the current solar cycle. to determine flows in the near-surface layers of the solar convection zone from the surface to a depth of about 16 mm, we have analyzed dopplergrams obtained with the global oscillation network group (gong) and the helioseismic and magnetic imager (hmi) onboard the solar dynamics observatory (sdo) using a dense-pack ring-diagram analysis. we will compare the zonal and meridional flows during cycle 24 with those during cycle 23. the zonal and meridional flows at high latitudes are now accessible thanks to hmi data. the zonal- and meridional-flow patterns track the mean latitude of activity and are precursors of magnetic activity appearing about three years before activity is visible in synoptic maps of the solar surface. the poleward branch of the zonal-flow pattern is noticeable during cycle 24 but is considerably weaker than during the previous cycle. we will also present the latest results from global helioseismology for comparison. | solar subsurface flows during solar cycle 24 |
the solar active region photospheric magnetic field evolves rapidly during major eruptive events, suggesting appreciable feedback from the corona. using high-cadence vector magnetograms, multi-wavelength coronal imaging, and numerical simulation, we show how the observed photospheric "magnetic imprints" are highly structured in space and time, and how it can in principle be used to estimate the impulse of the lorentz force that accelerates the coronal mass ejection (cme) plasma. in an archetypal event, the lorentz force correlates well with the cme acceleration, but the total force impulse surprisingly exceeds the cme momentum by almost two orders of magnitude. such a clear trend exists in about two thirds of the eruptions in our survey for cycle 24. we propose a "gentle photospheric upwelling" scenario, where most of the lorentz force is trapped in the lower atmosphere layer, counter-balanced by gravity of the upwelled mass. this unexpected effect dominates the momentum processes, but is negligible for the energy budget. we discuss how the upcoming high-sensitivity observations and new-generation numerical models may help elucidate the problem. | excess lorentz force in major solar eruptions |
we present the results on the analysis of microwave (mw) emission in solar flares related to strong solar energetic particle (sep) events observed during the 23rd solar cycle. the parameters of the mw spectrum were used as indicators of acceleration processes during solar flares. the magnetic topology of the active regions (ars) that produced the flares were taken into account by the approach suggested by abrameko et al. [2018]. we found that during their evolution most of the ars related to proton-rich sep events violated at least one of the classical sunspot group evolution laws (hale's law, joy's law et cetera). however, the statistical study of all ars of the cycle revealed the domination of normal ars. the dependences between sep events and mw indicators of the acceleration process for different groups are studied and discussed. | study on the features of the sep solar origin based on microwave observations |
solar corona plasma composition, derived from full-sun spectra, and the f10.7 radio flux (2.8 ghz) have been shown to be highly correlated (r = 0.88) during the recent weak solar cycle. however, this correlation becomes nonlinear at times of increased solar magnetic activity. we used co-temporal, high spatial resolution, radio (jvla), and euv (hinode/eis) images of the sun taken on the 3 and 7 april 2020 to understand the underlying causes of the non-linearity of the fip bias-f10.7 solar index correlation. we then calculated differential emission measures from aia images, and paired them with the observed fip bias to predict the bremsstrahlung component of f10.7 radio emission. results of this study provide constraints on the amplitude of composition variability related to solar cycle amplitude, and provide an alternative method to calculate coronal composition. | understanding the correlation between solar coronal abundances and f10.7 radio emission |
the sun's activity cycle governs the radiation, particle and magnetic flux in the heliosphere creating hazardous space weather while the decadal-scale variations define space climate and force the terrestrial atmosphere. predicting the solar cycle variations is challenging because of the unpredictable variations of parameters involved. thus study in variations of solar activity is important for understanding the underlying mechanism involved and for predicting the level of activity in view of the activity impact on space weather and global climate. by using the observed data of solar parameters viz. sunspot numbers, f 10.7cm index and lyman alpha index recorded for last seventy years (1947 - 2017) and applying the hodrick prescott filtering method to bifurcate each time series into cyclic and trend parts, we have predicted the trend of solar activities for solar cycles 25 & 26. during the analysis, the cyclic part of each time series was used to analyze the persistence while the trend part was used to obtain the input data for the study of future predictions. further, the cyclic component of each parameter was analyzed by using the rescaled range analysis and the value of hurst exponent was obtained for sunspot numbers, f10.7cm index and lyman alpha index as 0.90, 0.93 and 0.96 respectively. by using the simplex projection analysis on the values of amplitude and phase of the trend component of each time series, we have reconstructed the future time series representing solar cycles 25 and 26. when extrapolated further in time, the reconstructed series provided the maximum values of sunspot numbers as 89±9 and 78±7; maximum values of f10.7 cm index were 124±11 and 118±9 and lyman alpha index were 4.61±0.08 and 4.41±0.08 respectively for solar cycles 25 and 26. during analysis, we found that the solar cycle 25 will start in the year 2021 (january) and will last till 2031 (february) with its maxima in year 2024 (february) while the solar cycle 26 will start in the year 2031 (march) with its maxima in 2036 (june) and will last till the year 2041 (february).we have also compared the activities of solar cycles 5 & 6 (dalton minima periods) to solar cycles 25 and 26 and have inferred that the other solar minimum is underway. this is a clear indication of substantial weakening trend in solar activity which may lead to the speculation of other minima and cooling global climate. | predictions for solar cycles 25 & 26 - a substantial weakening trend in solar activity |
solar flares are an explosive manifestation of the complex magnetic structuring of active regions in the solar atmosphere. the photospheric magnetic field is found to change rapidly, abruptly, and significantly during flaring events. previous studies are mainly based on line-of-sight or low-cadence data. in this work, we focus on the temporal and spatial evolution of the permanent changes in the magnetic field of solar flares from high-cadence vector data (135 seconds) of the imaging system (dopplergrams and magnetograms) of the sdo/hmi instrument. the highly energetic events under analysis occurred during the solar cycle 24, covering low and high energy ranges, according to goes classification. this investigation also stands as a crucial input for the characterization and understanding of sunquakes. | photospheric magnetic field variation during solar flares and their implication for the generation of sunquakes |
the structure and evolution of the solar magnetic field is driven by a magnetohydrodynamic dynamo operating in the solar interior, which induces various solar activities that exhibit periodic variations on different timescales. therefore, probing the periodic nature of emission originating from the solar corona may provide insights of the convection-zone-photosphere-corona coupling processes. we present the study of the mid-range periodicities, between rotation period (∼27 days) and the schwabe cycle period (∼11 yr), in the solar soft x-ray emission, based on the data obtained by two instruments: sphinx and soxs in various energy bands. | periodicities in the x-ray emission from the solar corona: sphinx and soxs observations |
we present principal components analysis (pca) of temporal magnetic field variations over the solar cycles 21-24. these pcs reveal two main magnetic waves with close frequencies (covering 40% of data variance) travelling from the opposite hemispheres with an increasing phase shift. extrapolation of these pcs through their summary curve backward for 2000 years reveals a number of ~350-year grand cycles and about 2000 super-grand cycles superimposed on 22 year-cycles with the features showing a remarkable resemblance to sunspot activity reported in the past. the summary curve calculated forward for the next millennium predicts further three grand cycles with the closest grand minimum occurring in the forthcoming cycles 25-27 when the two magnetic field waves have a phase shift of 11 years. we explore a role of other independent components derived with pca and their expected effects on the resulting summary curve, or solar activity curve. we suggest that these grand and super-grand cycles can be produced by two dynamo waves generated in different layers with close frequencies whose interaction leads to beating effects that is discussed in the work by popova et al (2016) presented here. this approach opens a new era in investigation and prediction of solar activity on long-term timescales. | solar grand and super-grand cycles derived with pca from the solar background magnetic field |
the solar magnetic activity cycle provides energy input that is released in intense bursts of radiation known as solar flares. as such, the dynamics of the activity cycle is embedded in the sequence of times between the flare events. recent analysis [snelling et al., 2020, ashwanden and johnson, 2021] shows that solar flares exhibit memory on different timescales. information theory analysis shows that the time ordering of flare events is not random, but rather there is dependence between successive flares. the increased mutual information results from the clustering of flares, which we demonstrate by comparing the cumulative distribution function of successive flares with the cumulative distribution function of surrogate sequences of flares obtained by random permutation of flares within rate-variable bayesian blocks during which it is assumed that the flare rate is constant. differences between the cumulative distribution functions is substantial on a timescale around 3 hours, suggesting that flare recurrence on that timescale is more likely than would be expected if the waiting time were drawn from a nonstationary poisson process. at longer waiting times, the waiting time distribution of flares exhibits a power law form. the power laws also reveal memory in the nonlinear time dependence of the flaring rate. we discuss how time variability in the underlying driver of flares leads to power laws, and in particular discuss how sinusoidal or impulsive driving affects the waiting time distribution of flares. | memory and scaling laws in the dynamics of solar flares |
using a nonlinear force free field (nlfff) method to extrapolate photospheric magnetic fields, we compute the force free field parameter (α), which is a measure of torsion of the magnetic field lines. we calculated the α parameter for 62 active regions that produced major eruptive events in solar cycle 24. we verified statistically how the 62 studied active regions obey the hemispheric rule of helicity. in agreement with previous studies, we found that 67% of active regions located in the northern hemisphere have a negative sign for the global alpha parameter αg, and 69% of the active regions situated in the southern hemisphere have a positive sign. we have identified and analyzed five cases of evolution of αg at times when eruptive phenomena occurred in the selected active regions. we find that 52% of cases show an increase of torsion during flares, while only 22% show a decrease. this shows that increasing torsion plays an important role in flare ignition. for the other cases, a definitive conclusion cannot be reached because of multiple variations. | evolution of force free field parameter in active regions with major eruptive events |
the sun launches tangled masses of plasma and magnetic fields in the form of coronal mass ejections. but these explosions dont occur in a (literal or metaphorical) vacuum how is the passage of a coronal mass ejection affected by the eruptions that preceded it?capturing coronal mass ejectionsillustration of a coronal mass ejection headed toward earth. [soho/lasco/eit (esa nasa)]when the suns activity cycle ramps up to its maximum, as it will in 2025, the sun will unleash two or three coronal mass ejections every day. these explosions blast out into the solar system, speeding toward earth and the other planets at hundreds of kilometers a second. when a coronal mass ejection collides with earths protective magnetic field, the ensuing magnetic tussle can fling high-energy particles into earths atmosphere, creating the aurora and potentially damaging spacecraft electronics.given the risk of damaging effects on earth-orbiting spacecraft, researchers have developed models to predict the path a coronal mass ejection will take after detaching from the sun. these models estimate how a loop of magnetized plasma twists, expands, and is deflected as it travels through the tenuous swirls of the solar wind. however, many such models trade accuracy for speed in order to quickly assess the danger to earth, failing to capture the variable and turbulent nature of the space between sun and earth, which may affect how coronal mass ejections travel through that space.a series of solar eventsa team led by chin-chun wu (naval research laboratory) used magnetohydrodynamics simulations to explore how a coronal mass ejection moves through the wake left by previous solar eruptions. wu and collaborators opted to model a series of five coronal mass ejections that occurred in two and a half weeks in july 2012, for which we have extensive data.modeled radial solar wind speed for four time periods. the red areas indicate coronal mass ejections. click to enlarge. [adapted from wu et al. 2022; full time series available here]the teams model uses observations of these events to determine each coronal mass ejections initial speed, trajectory, and the time it departs the sun. by solving fluid dynamics equations to understand how each event evolves over time, the model outputs key parameters like the plasma density and temperature, the speed of the background solar wind, and the magnetic field strength, all of which can be compared against measurements made by satellites.creating a path to followobserved (black points) and modeled (red and purple lines) plasma parameters. the model results for a series of three coronal mass ejections are shown as red dotted lines, and the model results for a single coronal mass ejection are shown in purple lines. from top to bottom, the parameters shown are the radial velocity (vr), the plasma density (np), the plasma temperature (tp), and the magnetic field strength (b). click to enlarge. [wu et al. 2022]previous work has suggested that when one coronal mass ejection closely follows another, the second event moves faster than it would otherwise. to test this theory, wu and coauthors compared a model of a series of coronal mass ejections to another of just the final event in the series. these simulations showed that a coronal mass ejection following in the wake of other explosions travels faster than one forging ahead solo the passage of a previous shock wave reduces the density and increases the speed of the solar wind, allowing the final coronal mass ejection to surf its way to earths orbit 30 minutes faster.ultimately, the authors concluded that their model was able to match the observed parameters of the five coronal mass ejections fairly well. their simulations allowed them to show that coronal mass ejections are affected by those that came before, suggesting that multiple events should be accounted for in modeling these eruptions.citationmagnetohydrodynamic simulation of multiple coronal mass ejections: an effect of pre-events,' chin-chun wu et al 2022 apj 935 67. doi:10.3847/1538-4357/ac7f2athe post one after another: the effect of repeated coronal mass ejections appeared first on aas nova. | one after another: the effect of repeated coronal mass ejections |
because venus has no strong planetary magnetic field, the fast-flowing solar wind plasma can propagate to regions close to the planet. therefore, understanding the distribution of hot atomic oxygen in the corona and the resulting pickup of oxygen ions is essential in characterizing the dynamics of the venusian upper atmosphere and that of the overall planet's interaction with the plasma of the ambient solar wind. the work presented here is focused on characterizing how the hot oxygen corona changes during a solar cycle. that involves numerical modeling not only of the corona itself but also the thermosphere and ionosphere. each of the models employed in this study covers a physical sub-domain such that the coupled combination of the codes self-consistently describes the studied environment. the physical sub-domains are organized such that (1) vtgcm produces a self-consistent calculation of the thermosphere/ionosphere providing spatial distribution of the thermal oxygen as well as all the dominant species, (2) the calculated distribution of the major species is further used to model the three-dimensional hot oxygen corona with amps. these results will be used as input to a full mhd simulation of the solar wind/venus interaction. here, we present recent results of a hot oxygen corona calculation in 3d and its variation with solar activity. we use a 3d thermosphere/ionosphere model to calculate both the source of hot o in the dissociative recombination of o2+ ions and the upper thermosphere distributions of co2, co, n2, and thermalized o through which the nascent hot o must pass before reaching the corona. support for this work is provided by nasa grant 80nssc17k0728 from the solar system workings program. | variability of venusian hot oxygen corona during a solar cycle |
the relationship between coronal mass ejections (cmes) and corresponding x-ray flares was studied for the time interval covering cycle 23 and the beginning of cycle 24 (1996-2013). it is shown that the energy difference between cmes and associated flares is larger at the decline of the solar cycle than in its rise phase. a similar relation is observed between the cme velocity (energy) and the effective solar multipole index, which characterizes the typical size of elements of the system of large-scale solar magnetic fields. this suggests that cmes are mostly associated with individual active regions at the minimum and rise of the 11-year cycle, while the cme energy is mostly determined by active region complexes at the maximum and in the declining phase. | variations in the relationship between coronal mass ejections and corresponding x-ray flares during the 11-year solar activity cycle |
we present our recent effort to implement modern variational data assimilation techniques into a 2.5 d mean field solar dynamo code. this work extend the work of (jouve et al. 2011, apj) to take into account the correct spherical geometry and meridional circulation into so-called babccok-leigthon flux transport dynamo models. based on twin-experiments, in which we observe our dynamo simulations, and on a well defined cost function using toroidal and poloidal field observations we are able to recover the main attributes of the dynamo solution used to test our data assimilation algorithm. by assimilating solar data (such as wolf number or butterfly diagram) we are starting to deduce the profile and temporal variations of key ingredients of the solar dynamo. we find that the data sampling and the temporal window are key to get reliable results. we show how such powerful technique can be used to improve our ability to predict the solar magnetic activity. this work is supported by idex sorbonne paris cite via the damse project. | improving solar 11yr magnetic cycle prediction by using variational data assimilation in a mean field dynamo model |
solar cycle 24 is characterized by relatively weak sunspot activity and is developing according to the smallest cycle scenario (svalgaard, cliver, and kamide, 2005). using the solar dynamics observatory (sdo) data for may 2010-september 2014, we present the results of a study of solar cycle 24 in the photosphere and corona during the ascending and maximum epochs. these data have been prepared in the form of synoptic maps (one map corresponds to one solar rotation) as functions of latitude and longitude for carrington rotations cr2097-cr2154. to study the axisymmetric structure of the cycle, the maps have been averaged over longitude. solar activity pulses, which are visible in an axisymmetric midlatitude magnetic flux, correspond to coronal brightening events in the extreme ultraviolet in the 193 å band. solar cycle 24 is characterized by weak magnetic polar activity, weakly pronounced high-latitude waves of coronal activity, and north-south asymmetry in the sign change of the polar solar magnetic field, which is directly connected with the asymmetry in an emerging magnetic flux in the region of sunspot activity and, hence, solar activity pulses. thus, the north polar field became mainly positive in the latitude zone from 75.01° to 79.73° in 2013, while the south field started changing sign in september 2014. | pulsed nature of solar cycle 24 |
surface flows have played essential roles in predicting solar cycles and connecting the signatures of the solar dynamo. in order to provide the surface flows, such as meridional flows, differential rotation, and zonal flows, in 10 solar cycles, as input for the dynamo and solar cycle modeling, we track the flows from halpha images as a proxy for magnetic features using local correlation tracking (lct) tool. in this work, we present the preliminary result of the derived flow maps using the halpha data from kanzelho ̈he solar observatory (kso). the correlation between the chromospheric flows and surface flows makes deriving the surface flows on a wide range of time-scales achievable. we aim to provide the long-term observational constraints of surface flows, including hemispheric and latitudinal dependence. | study of global-scale surface flows of the sun in past 10 solar cycles |
since 2008 the hinode spacecraft has been taking monthly synoptic high-resolution spectropolarimetric observations of the central meridian of the sun. this data provides routine observations of small-scale magnetism from pole to pole. in this project we search this unique dataset for variation of the small-scale magnetic field from one solar minimum to the next. by doing so, we investigate whether the small-scale magnetism varies in the same time scales as the large-scale magnetic field, which is still an unanswered question. our future goal is to establish a connection between the large-scale solar dynamo on local dynamo action, which is shown in simulations. as of now, we have a magnetic butterfly diagram covering the period from june 2008 to march 2020. the multi-scale connection could have consequences for the overall magnetic behavior of the sun during periods of extended low activity such as the maunder minimum of 1645-1715, and on the solar irradiance and earth climate during these periods. | variation of small-scale solar magnetic fields with hinode |
the analysis of the movements of the solar photosphere has been used by several authors to study the dynamics of solar plasma at various spatial and temporal scales. this work, in particular, is focused on the study of vertical movements, in order to perform a statistical analysis of the flow maps to characterize some dynamic aspects of the photospheric plasma along the time evolution of the sun. to carry out this analysis, we used a set of images obtained by the hmi instrument hmi (helioseismic and magnetic imager) aboard the sdo mission (solar dynamics observatory) to which local correlation tracking algorithms (lct) were applied. they allow the identification of areas of convergence and divergence of the plasma at certain time intervals during the solar cycle 24, thus covering moments of high and low solar activity. the study gives us the reason for the meridional movements showing that in low latitudes the outgoing emergency flow occupied a higher percentage of area, while in the latitudes near the poles the behavior changes, that is, the incoming flows occupy a greater area. | analysis of large-scale photospheric dynamics during the solar cycle 24 |
radial diffusion has been established as one of the most important mechanisms contributing the acceleration and loss of relativistic electrons in the outer radiation belt. over the past few years efforts have been devoted to provide empirical relationships of radial diffusion coefficients (dll) for radiation belt simulations yet several studies have suggested that the difference between the various models can be orders of magnitude different at high levels of geomagnetic activity as the observed dll have been shown to be highly event-specific. in the frame of safespace project we have used 12 years (2009 - 2020) of multi-point magnetic and electric field measurements from themis a, d and e satellites to create a database of calculated dll. in this work we present the first statistics on the evolution of dll during the various phases of solar cycle 24 with respect to the various solar wind parameters and geomagnetic indices.this work has received funding from the european union's horizon 2020 research and innovation programme "safespace" under grant agreement no 870437. | radial diffusion coefficients database in the frame of safespace project |
observations of the photosphere, chromosphere, and corona combined with magnetic field modeling of one of the biggest sunspots of the 24 solar cycle, revealed that regions of high fip bias plasma in the corona were magnetically linked to the locations of the intrinsic magnetic oscillations in the solar chromosphere. in order to characterize the driver of the oscillations, we analyzed the relation between the spatial distribution of the magnetic wave power and the overall field geometry and plasma parameters obtained from the multi-height spectropolarimetric non-local thermodynamic equilibrium (nlte) inversions. in correspondence with the locations where the magnetic wave energy is observed at chromospheric heights, we found evidence in support of locally excited acoustic waves that, after crossing the equipartition layer located close to the umbra-penumbra boundary at photospheric heights, are converted into magnetic-like waves. these results indicate a direct connection between sunspot chromospheric activity and observable changes in coronal plasma composition, demonstrating the power of high resolution, multi-height studies of the solar atmosphere that will become the gold standard in the era of dkist. | investigating of the nature of magnetic oscillations associated with fip effect |
at the end of last year, the suns large-scale magnetic field suddenly strengthened, reaching its highest value in over two decades. here, neil sheeley and yi-ming wang (both of the naval research laboratory) propose an explanation for why this happened and what it predicts for the next solar cycle.magnetic strengtheninguntil midway through 2014, solar cycle 24 the current solar cycle was remarkably quiet. even at its peak, it averaged only 79 sunspots per year, compared to maximums of up to 190 in recent cycles. thus it was rather surprising when, toward the end of 2014, the suns large-scale magnetic field underwent a sudden rejuvenation, with its mean field leaping up to its highest values since 1991 and causing unprecedentedly large numbers of coronal loops to collapse inward.yet in spite of the increase we observed in the suns open flux (the magnetic flux leaving the suns atmosphere, measured from earth), there was not a significant increase in solar activity, as indicated by sunspot number and the rate of coronal mass ejections. this means that the number of sources of magnetic flux didnt increase so sheeley and wang conclude that flux must instead have been emerging from those sources in a more efficient way! but how?aligned activitywso open flux and the radial component of the interplanetary magnetic field (measures of the magnetic flux leaving the suns photosphere and heliosphere, respectively), compared to sunspot number (in units of 100 sunspots). a sudden increase in flux is visible after the peak of each of the last four sunspot cycles. click for a larger view! [sheeley wang 2015]the authors show that the active regions on the solar surface in late 2014 lined up in such a way that the emerging flux was enhanced, forming a strong equatorial dipole field that accounts for the sudden rejuvenation observed.interestingly, this rejuvenation of the suns open flux wasnt just a one-time thing; similar bursts have occurred shortly after the peak of every sunspot cycle that we have flux measurements for. the authors find that three factors (how the active regions are distributed longitudinally, their sizes, and the contribution of the axisymmetric component of the magnetic field) determine the strength of this rejuvenation. all three of these factors happened to contribute optimally in 2014.as a final note, sheeley and wang suggest that the current strength of the axisymmetric component of the magnetic field can be used to provide an early indication of how active the next solar cycle might be. using this method, they predict that solar cycle 25 will be similar to the current cycle in amplitude.citationn. r. sheeley jr. and y.-m. wang2015 apj 809 113. doi:10.1088/0004-637x/809/2/113 | witnessing solar rejuvenation |
we measure the sunspot areas of activity cycle 24 using ten years of continuum images from the helioseismic imager (hmi), and compare them with the peak flare soft x-ray flux from the geostationary operational environmental satellite (goes). we find that the maximum area reached by sunspots in our sample is positively correlated with the magnitude of the largest flare they produce. complex spot groups with magnetic classification tend to be larger and more likely to produce intense flares. our findings are consistent with previous studies. | the dependence of solar flare magnitude on sunspot area during activity cycle 24 |
in this talk, i will discuss the cosmic ray solar diurnal anisotropy measurements using the data recorded by the grapes-3 muon telescope over two 11-year solar cycles (2001-2021). the grapes-3 muon telescope records 4 billion muons every day, probing a tiny variation in cosmic ray flux caused by solar activity. in the first part of my talk, i will discuss the efficiency and pressure correction analysis of the muon data, followed by a discussion on the extraction of solar diurnal anisotropy parameters using fourier techniques. the yearly and monthly averages of solar diurnal anisotropy amplitude have strongly dependent on the interplanetary magnetic fields measured by nasa satellites located at the first lagrangian point. the annual phase variation of the diurnal anisotropy suggests its dependence on the 22-year solar magnetic cycle than the 11-year sunspot cycle. | long term measurements of cosmic ray solar diurnal anisotropy |
the properties of the solar constant variability are considered according to the results of satellite observations (http://lasp.colorado.edu/home/sorce/data/tsi-data/). the obtainment of satellite data with an accuracy of 0.01% that is devoid of atmospheric influence allows a detailed analysis of variations in this index of solar activity and space weather for solar-activity cycles 21-24. the use of wavelet analysis demonstrates the properties of the 11-year cycle in the variation of the solar constant. with the exclusion of variations of the 11-year cycle, it is possible to study short-period processes in each solar cycle. the variations in the solar constant demonstrate their own local spectrum of power periods, which differs from the activity periods according to sunspot observations. the most significant decrease in the solar constant occurs during the passage in the center of the solar disk of large groups of spots and activity complexes that block the solar constant. thus, the basic properties of the intrinsic variability of the solar constant differ from the properties of the magnetic cycle. | properties of the variability of the solar constant as an index of solar activity |
the solar activity evolves over a cycle of about 11 years recognized as the shwabe cycle. where the solar activity level is measured by the number of observed sunspots on the solar surface. the high activity emanating from the sun may impacts the magnetic environment around the earth as the the horizontal component of the earth magnetic field. in this work we show the great correlation between the schwabe cycle 24 and the cyclic variation of the horizontal component. however we compute the monthly arithmetical mean variation of the horizontal component lasting along the solar cycle 24. the data are provided by tam observatory (algeria) and obtained from the intermagnet network. the illustration of the cyclic evolution of the horizontal component displays clearly the evolution of magnetic perturbations according to the minimum and the maximum of solar activity. it also clearly displays the double pics perturbations occurred at solar maximum on 2012 and 2014. | the correlation of the schwabe cycle of solar activity and the cyclic variation of the horizontal component of the emf |
changes of the energy flux in the convection zone can lead to variations of the total solar electromagnetic output, the solar luminosity, on time scales from decades to millennia. in fact, space-based observations of the total and spectral solar irradiance are observed to follow the solar cycle activity. however, these observations can not be employed to estimate directly the solar luminosity because they cover just a small latitudinal region near the ecliptic plane. recently, vieira et al. (2012) employed a semi-empirical model to estimate the flux density for the whole sphere based on observations of the distribution of magnetic field on the solar surface from sep/2010 to apr/2012. here we present a reconstruction of the solar luminosity for the solar cycles 23-24. the reconstruction is based on a combination of a state-of-art solar surface magnetic flux transport model (schrijver and derosa, 2003) and a semi-empirical model of the total and spectral irradiance. the estimate of the flux density indicates that the heat flux blocked by sunspots is lower than the flux leaked by bright features. consequently, an increase of the luminosity through the cycle is observed as previously estimated based on near ecliptic measurements. we discuss in details the limitations of the model and future strategies to extend the reconstruction of the flux density and solar luminosity in time scales from decades to millennia. | variability of the solar luminosity during cycles 23 and 24 |
solar active region (ar) 12192 of october 2014 hosts the largest sunspot group in 24 years. it is the most prolific flaring site of cycle 24, but surprisingly produced no coronal mass ejection (cme) from the core region during its disk passage. here, we study the magnetic conditions that prevented eruption and the consequences that ensued. we find ar 12192 to be "big but mild"; its core region exhibits weaker non-potentiality, stronger overlying field, and smaller flare-related field changes compared to two other major flare-cme-productive ars (11429 and 11158). these differences are present in the intensive-type indices (e.g., means) but generally not the extensive ones (e.g., totals). ar 12192's large amount of magnetic free energy does not translate into cme productivity. the unexpected behavior suggests that ar eruptiveness is limited by some relative measure of magnetic non-potentiality over the restriction of background field, and that confined flares may leave weaker photospheric and coronal imprints compared to their eruptive counterparts. | why is the great solar active region 12192 cme-poor? |
we examine alfvénic fluctuations within the interplanetary coronal mass ejections (icme) and high-speed streams (hss), and their effects to geomagnetic activity during the solar cycle 23. we show that a rapid transition from the predominance of slow (< 400 km/s) to fast (> 600 km/s) alfvénic fluctuations during early declining phase of the solar cycle 23 coincides with the rapid increase of geomagnetic activity in 2003. we found out that solar wind is roughly twice as alfvénic during high-speed streams, which dominate the declining solar cycle phase, than during interplanetary coronal mass ejections, which occur more frequently during solar maxima. furthermore, interplanetary coronal mass ejection -related solar wind is alfvénic only for a few hours during their passage, while high-speed stream -related alfvénic fluctuations last typically for several days, making high-speed streams powerful in modulating high-latitude geomagnetic activity. | alfvénic fluctuations of icmes and high-speed solar wind streams |
the climate system plays an important role in the geomorphological dynamics of a region. the cold, arid, high altitude, tectonically active areas of ladakh (india) in trans himalaya, western tibetan plateau is none exception. noticeable change in the landscape with a shift from fluvial to lacustrine regime at 10000 yrs bp forming big open valley lakes occupying the present day river valleys is attributed to the early holocene northward advancement of the mean latitudinal position of the summer itcz causing wetter conditions in this dry area. the glaciers of the ladakh range are almost depleted and the northern range glaciers show andrastic retreat in the quaternary time. lakes were studied using multi-proxies, to record centennial and decadal scale climatic variability. spatial and temporal setting of spituk palaeolake (12600-240 cal yrs bp) along indus river, was analyzed using multi proxies. the lake that extended for 40-50 km covering an area of 106 km2, was formed after older dryas as a result of river blockage by precipitation induced debris flow and seismicity. two lake phases between 12600-9000 and 5500-3200 cal yrs bp show stable lake conditions and have synchronous relationship between high variation in monsoon intensity, high δ18o values in the guliya core, rise in temperature and high solar insolation. high magnetic susceptibility and clay content along with diversified diatom and other freshwater algae and land derived organic matter are indicative of fresh water supply leading to high lake level from 4700 yr bp onwards in the present pro-glacial lakes studied. the multi-proxy data provides evidence of much higher and stable lake level during 3700 yr bp and 3000 yr bp onwards due to high water supply in these lake. it is in contrast to the records of weak ism conditions and low lake level in rest of the part of indian peninsula during the period. the study also suggests strong western disturbance activity during 4800-3000 yr bp leading to high lake level in this region. the ongoing researches aim to make an inventory/dataset of these records and address the climate-tectonics interaction with respect to the lake outburst consequences. | climate and tectonic variability during late quaternary in western fringe of tibetan plateau: case study from trans-himalayan ranges of ladakh, nw india |
techniques in local solar seismology applied to observations of seismic oscillations in the sun's near hemisphere allow us to map large magnetic regions in the sun's far hemisphere. seismic signatures are not nearly as sensitive to magnetic flux as observations in electromagnetic radiation. however, they clearly identify and locate the 400 or so largest active regions in a typical solar cycle, i.e., those of most concern for space-weather forecasting. by themselves, seismic observations are insensitive to magnetic polarity. however, the hale polarity law offers tantalizing avenues for guessing polarity distributions from seismic signatures as they evolve. i will review what we presently know about the relationship between seismic signatures of active regions and their magnetic and radiative properties, and offer a preliminary assessment of the potential of far-side seismic maps for space-weather forecasting in the coming decade. | advances in predicting magnetic fields on the far side of the sun |
using a series of vector magnetograms in spaceweather hmi active region patch (sharp) format, for two hours before and after the solar flare, we calculated the magnetic flux using a nonlinear force-free field (nlfff) method. we calculated the magnetic flux for 62 active regions that produced strongest flares in solar cycle 24 and identified five cases of evolution. we found that in most cases are increases in magnetic flux values during eruptions, this indicates that the onset of the eruption is correlated with the evolution of the magnetic flux. | evolution of magnetic flux in solar active regions with strongest flares |
solar transients are responsible for initiating short - term and long - term variations in earth's magnetosphere. these variations are termed as geomagnetic disturbances, and driven by the interaction of solar wind features with the geo-magnetosphere. the strength of this modulation process depends upon the magnitude and orientation of the interplanetary magnetic field and solar wind parameters. these interplanetary transients are large scale structures containing plasma and magnetic field expelled from the transient active regions of solar atmosphere. as they come to interplanetary medium the interplanetary magnetic field drape around them. this field line draping was thought as possible cause of the characteristic eastward deflection and giving rise to geomagnetic activities as well as a prime factor in producing the modulation effects in the near earth environment. the solar cycle 23 has exhibited the unique extended minima and peculiar effects in the geomagnetosphere. selecting such transients, occurred during this interval, an attempt has been made to determine quantitative relationships of these transients with solar/ interplanetary and geophysical parameters. in this work we used hourly values of imf data obtained from the nssd center. the analysis mainly based on looking into the effects of these transients on earth's magnetic field. the high-resolution data imf bz and solar wind data obtained from wdc-a, through its omniweb, available during the selected period. dst and ap obtained from wdc-kyoto are taken as indicator of geomagnetic activities. it is found that dst index, solar wind velocity, proton temperature and the bz component of magnetic field have higher values and increase just before the occurrence of these events. larger and varying magnetic field mainly responsible for producing the short-term changes in geomagnetic intensity are observed during these events associated with coronal holes. | solar wind plasma flows and space weather aspects recent solar cycle |
recently atmospheric re-entry technology becomes important because some deep space sample return missions and manned and unmanned space vehicles are under developing for manned/unmanned moon and mars exploration during 2030's and 2030's, and space tourism and especially space manufacturing as taking advantages of micro gravity environment. for the design of space re-entry vehicle we should know the vertical distribution of physical properties such as temperature, pressure, density and molecular weight between the range of 0 ~ 300 km. the physical parameters are varied with local time, seasons, earth's magnetic activities and solar activities such as 11 year variation cycle. fortunately there has been many researches since 60's on the atmospheric modelling through empirical and combining theoretical & empirical models, such as nrlmise, etc. using these models we establish a data sets from various local time, seasons and solar activities. and we use an interpolation technique to get the data for a certain local time, seasons and solar activities. for practical and actual utilization, it is very much required to verify the data base. therefore we get some data sets from ground/space observations through lidar, hf radar and optical spectrometers. in conclusion the data sets from modelling are well matched with actual observation data sets. | comparisons of modelling atmosphere and observation data between range of 0300 km altitude for re-entry utilization |
using plasma measurements from the cnes demeter micro-satellite, we have performed a global survey of ionospheric disturbances observed at middle and low latitudes on the nightime part of the demeter orbit in the local time sector 21.30-22.30 lt. this study encompasses the 6 years of the satellite operations, from 2005 to 2010, including years of moderate magnetic activity of solar cycles 23 and 24 and the deep solar minimum in 2009-2010. we report in this poster a statistical analysis of mstid events characterized by quasi-periodic variations of the o+ density observed below ~ 40° geomagnetic latitudes with wavelengths ranging from 350 to 700 km. although detected in both hemispheres they occur predominantly at southern latitudes with a rather strong peak over the pacific ocean. a detailed analysis has shown that these events may be sorted in 4 categories according to their latitudinal extent. most of them are restricted to a latitude band between ~ 15° and 40° geomagnetic in north or south but some of them extend from mid latitudes in one hemisphere to low latitude in the other hemisphere, thus spanning equatorial regions up to 5-10°. the apparent negative correlation with magnetic activity seems to indicate that most of these events are driven by agw originating from low altitude atmospheric levels and not triggered by auroral phenomena. we shall present the seasonal and inter-annual variations showing significant changes associated with solar activity. our results will be compared to other ground-based or satellite observations and our investigation pointed out a strong effect of these mstid and their parent agw on the electrodynamics of the low latitude ionosphere. | climatology of mid-latitude mstid events observed by the demeter satellite in the period 2005-2010. |
the explanation for the observed phenomenon of repeated maxima of sunspot cycles is proposed. key roles in the proposed scenarioplay two tides of toroidal field from the lower base of the solar convection zone (scz) to the surface. deep toroidal field is excited due to ω-effectnear the bottom of the scz at the beginning of the cycle. then this field is transported to the surface due to combined acting of magnetic buoyancy,magnetic ∇ρ-flow and turbulent diamagnetism in the equatorial domain. over time the magnetic fragments can be seen as bipolar spots in themiddle latitudes in the "royal zone". this first wave of toroidal field, which is directed up, gives the main maximum activity spots. however, theunderlying toroidal field in the high-latitude polar domains at the beginning of the cycle is blocked by directed downward magnetic∇ρ-pumping and turbulent diamagnetism. directed to the equator deep meridional flow replaces this field to the low latitudes (the equatorialdomain) during about 1 - 2 years. after that the turn of floating this "retarded" field to surface (second tide of toroidal field). coming to the surfaceat low latitudes this second portion of toroidal field leads to second sunspot maximum. | repeated maxima of sunspot cycles |
here, we present a study of ionospheric convection at high latitudes that is based on satellite measurements of the electron drift instrument (edi) on-board the cluster satellites, which were obtained over a full solar cycle (2001-2013). the mapped drift measurements are covering both hemispheres and a variety of different solar wind and interplanetary magnetic field (imf) conditions. the large amount of data allows us to perform more detailed statistical studies. we show that flow patterns and polar cap potentials can differ between the two hemispheres on statistical average for a given imf orientation. in particular, during southward directed imf conditions, and thus enhanced energy input from the solar wind, we find that the southern polar cap has a higher cross polar cap potential. we also find persistent north-south asymmetries which cannot be explained by external drivers alone. much of these asymmetries can probably be explained by significant differences in the strength and configuration of the geomagnetic field between the northern and southern hemisphere. since the ionosphere is magnetically connected to the magnetosphere, this difference will also be reflected in the magnetosphere in the form of different feedback from the two hemispheres. consequently, local ionospheric conditions and the geomagnetic field configuration are important for north-south asymmetries in large regions of geospace. the average convection is higher during periods with high solar activity. although local ionospheric conditions may play a role, we mainly attribute this to higher geomagnetic activity due to enhanced solar wind - magnetosphere interactions. | interhemispheric differences and solar cycle effects of the high-latitude ionospheric convection patterns deduced from cluster edi observations |
context. we apply our recently developed method to reconstruct synoptic maps of the photospheric magnetic field from observations of chromospheric plages and the magnetic polarity of sunspots. here, we apply the method to an extended time interval from 1915 to 1985.aims: systematic magnetographic observations of the solar photospheric magnetic field were initiated as recently as the 1970s and the lack of earlier observations limits our ability to study and understand the long-term evolution of the solar global field. this study is aimed at creating synoptic maps of magnetic fields for the pre-magnetograph era and using these maps as input for modern simulation models to investigate the long-term (centennial) evolution of the sun's global magnetic fields.methods: we reconstructed active solar regions by identifying chromospheric plages from ca ii k line synoptic maps and assigning magnetic polarities based on the observed polarity of sunspots. we used a surface flux transport (sft) model to simulate the evolution of the photospheric magnetic field from the reconstructed active regions. we used the potential field source surface (pfss) model to determine the amount of open magnetic flux from the reconstruction and from magnetographic observations. we also reconstructed the coronal field during two eclipses and compared the result with eclipse drawings.results: we successfully reconstructed the photospheric magnetic field from 1915 to 1985. the number and total magnetic flux of the reconstructed active regions shows a realistic cyclic behavior that mostly follows the evolution of the sunspot number, even on relatively short timescales. the polar field strengths of cycles 19 and 20 do not reflect the evolution of the sunspot number very accurately, which may be related to problems related to the calcium data during cycle 19 and the long data gap during cycle 20. the polarity of polar fields and the amount of open field both at high and low latitudes all demonstrate the expected cyclic behavior. the agreement of the modeled coronal structure with eclipse drawings in 1922 and 1923 is fair. | reconstructing solar magnetic fields from historical observations. ix. the photospheric magnetic field from 1915 to 1985 |
the solar corona is a highly dynamic environment which exhibits the largest releases of energy in the solar system in the form of solar flares and coronal mass ejections. this activity predominantly originates from active regions, which store and release free magnetic energy and dominate the magnetic face of the sun. active regions can be long-lived features, being affected by the sun's convective flows, differential rotation and meridional flows. the sun's global coronal field can be seen as the superposed growth and subsequent diffusion of all previously formed active regions. this talk will look at active regions as an observable product of the solar dynamo and will discuss the physical processes that are at play which lead to the storage and release of free magnetic energy. what happens to flux that emerges into the corona so that it goes down an evolutionary path that leads to dynamic activity? and how does this activity vary with active region age? when an active region reaches the end of its lifetime, his much of the magnetic flux is recycled back into subsequent solar cycles? the current status of observations and modelling will be reviewed with a look to the future and fundamental questions that are still be be answered. | the evolution of active regions |
magnetospheric ions with energies less than tens of ev originate from the ionosphere. the low energy indicates the origin of the plasma but also severely complicates detection of the positive ions onboard sunlit spacecraft at higher altitudes, which often become positively charged to several tens of volts. we discuss some methods to observe low-energy ions, including a technique based on the detection of the wake behind a charged spacecraft in a supersonic flow. low-energy ions typically dominate the density and flux in large regions of the terrestrial magnetosphere, also at high altitudes. this is true both on the nightside and the dayside, during all parts of the solar cycle. the loss of this initially low-energy plasma to the solar wind is one of the primary pathways for atmospheric escape. the global outflow is of the order of 1026 ions/s and often dominates over the outflow at higher energies. the outward flux increases by a factor of 2 with increasing solar euv flux during a solar cycle. the total outward flux may increase another factor of 2 due to an increased polar cap area at high geomagnetic activity. on the dayside, the increased density due to low-energy plasma will lower the alfvén velocity and the magnetopause reconnection rate. in addition, the low-energy ions with a gyro radius between the gyro radii of electrons and hot ions introduce a new lengths scale important for magnetic reconnection and hall currents. | low-energy ions as a major source of magnetospheric plasma: statistics and consequences |
active sand dune fields in cold climate regions commonly incorporate snow and ice from winter precipitation into their internal structure. sediment transported by dune movement can bury snow, protecting it from solar input and warming. the hydrological importance of this system is not well studied, in particular the ability of such a system to trap and preserve ice that may be later be as stored groundwater. this ice trap may be important for understanding desert ecosystems on earth, but may also represent an analog mechanism for buildup of ice below the mid-latitude surface of mars. electrical resistivity tomography (ert) imaging was used to investigate the depths of a dune for ice layers in the red desert, wyoming. data loggers were used to monitor the temperatures and moisture contents of the subsurface surrounding directly observed ice lenses within the dune. the ert survey revealed that subsurface ice lenses are not incorporated into the dune over long periods. this was consistent with the results of two consecutive seasons of data logger data, which revealed a three-stage life cycle of the ice lense, with eventual complete disappearance of ice in the dune by the end of the warm seasons. nuclear magnetic resonance (nmr) logging revealed an increasing water content of the dune with depth under ice lenses. this transport and entrapment mechanism for protected snow represents a possible explanation for observations of shallow subsurface ice at mid latitudes on mars. | martian analog hydro-geophysics in the red desert |
the photospheric magnetic field of a solar flaring active region is often observed to change quickly during major flares, by hundreds of gauss over timescales ranging from less than a minute to tens of minutes. permanent stepwise flare-related changes are generally more pronounced in the horizontal than in the vertical field component. near major magnetic neutral lines the horizontal component tends to increase abruptly early during the flare, whereas in sunspot penumbrae the horizontal component is often observed to decrease. this contrasting pattern is often accompanied by a 'halo' of decreasing horizontal field around the neutral line. here we analyze 15 x-class flares in 11 active regions featuring coherent lorentz force and magnetic shear changes at strong, sheared magnetic neutral lines and in twisted sunspots, as observed observed by the helioseismic and magnetic imager during cycle 24. an overview of the interrelated behavior of neutral-line and sunspot fields during major flares is given. | photospheric lorentz force and magnetic shear and twist changes during major cycle 24 flares |
the goal of the iswat h3 cluster is to understand, characterize and predict the fluxes of the two major sources of energetic particle radiation in the heliosphere, solar energetic particles (seps) and galactic cosmic rays (gcrs). solar energetic particles are protons, heavier ions and electrons that are accelerated by solar flares and shocks driven by coronal mass ejections, and have energies from 10s of kevs to gevs. they occur sporadically, and can lead to intense but temporary increases in radiation levels in the heliosphere that can commence with little (~few minutes) warning. their occurrence rate follows the ~11-year solar activity cycle. being charged, seps gyrate around and follow the spiral interplanetary magnetic field lines such that the largest particle fluxes tend to follow flares and cmes on the western hemisphere of the sun relative to the observer. however, seps can be distributed more widely in the heliosphere indicating that additional transport processes, often modeled as diffusion, take place either near the sun or in the solar wind. however, these processes that spread particles are poorly understood at present. the processes accelerating seps, such as reconnection in solar flares or acceleration by cme-driven shocks, are also under debate. in addition, theories of particle acceleration by shocks may require the presence of a "seed population", i.e., suprathermal particles at the sun and/or in the interplanetary medium that are difficult to quantify. thus, the successful prediction of the contribution of seps to the radiation environment in the heliosphere is challenging because there is much uncertainty in fundamental processes involved, and little forewarning of when an sep event will occur. galactic cosmic rays are particles with high energies (100s of mev to gev energies) accelerated by supernova-driven shocks, and enter the heliosphere from the interstellar medium. once in the heliosphere, they are subject to transport processes that are dominated by the large-scale structure of the interplanetary magnetic field and its variation follows the solar activity cycle. this gives rise to solar-cycle variations in the gcr intensity that are anti-correlated with solar activity and related to the direction of the global solar magnetic field. however, these variations in the gcr flux are reasonably well characterized so that when assessing radiation hazards, the risk from gcrs can be more easily predicted and mitigated by limiting the duration of exposure and adopting optimized shielding protection design. this presentation will discuss the aims and action topics of the iswat h3 cluster to improve the understanding of seps and gcrs and also to prepare for mitigating radiation risks associated with human space explorations. | iswat h3: radiation environment in heliosphere: seps and gcrs |
magnetospheric ultralow frequency (ulf) waves are known to be excited by various transient solar wind, foreshock and magnetosheath phenomena. in the absence of any upstream driving at specific frequencies, radially standing fast mode waves between the magnetopause and a turning point are often invoked to explain observed discrete frequency field line resonances. applying the theory of these coupled fast mode resonances (cfmrs) to a realistic magnetic field model and magnetospheric density profiles observed over almost half a solar cycle, we investigate the magnetospheric and solar wind factors that control their occurrence probabilities, locations and frequencies. we find that the dawn-dusk asymmetry in magnetospheric density profiles results in cfmrs being more likely around dawn. more generally, the probability of cfmr increases with distance between the magnetopause and the alfvén speed's local maximum. the latter's location depends on magnetospheric activity: during high activity it is situated slightly outside the plasmapause, whereas at low activity it is found at much larger radial distances. the frequencies of cfmr are proportional to the alfvén speed near the magnetopause, which is affected by both density and magnetic field variations hence exhibit considerable spread. the location of the excited resonance, and thus the penetration of fast waves into the magnetosphere, however depends on the relative steepness of the alfvén speed radial profile. the steeper this is, the closer the resonance is to the outer boundary and vice versa. these numerical calculations applied to realistic densities and magnetic fields over a wide range of conditions have revealed a number of predictions concerning ulf wave behaviour in the outer magnetosphere which may be tested against observations and applied to ulf wave driving models. | magnetospheric and solar wind dependences of coupled fast-mode resonances |
the century long (1907-2007) cak spectroheliograms from kodaikanal solar observatory (kso) were calibrated, processed and analysed to study the the evolution plages, a possible representative of magnetic activity on the sun. this has been the longest dataset studied in cak till date covering about 9.5 cycles of 11 year periods. plages were segmented with area > 1 arcmin2 using global thresholds for individual full disc images and subsequent application of morphological closing. plage index was calculated and seen to have close positive correlation with fractional plage area. obtained plage area cycle was compared with the same from mount wilson observatory (correlation 94:7%) for the overlapping period 1915-2000. study illustrated time-latitude distribution of plage centroids rendering butterfly diagram (as observed for sunspots) and its 3d visualization combining the individual plage areas. this study further delineated positional correlation between magnetic patches and plage regions through comparison of synoptic maps derived from both kodaikanal cak images and space based full disc los (line of sight) magnetograms. magnetograms from ground based observatories being available after 1950, this long term cak data from kso can be used as a proxy for estimating magnetic activity locations and their strengths at earlier times. | long term variation study of the sun from kodaikanal digitised data |
through variations in its magnetic activity at different timescales, the sun strongly influences the space weather conditions throughout the heliosphere. the most known solar activity variation is the schwabe cycle, also known as the sunspot cycle (scs), period of which ranges from 9 to 13 years. the sun also shows shorter quasi-periodic variations, such as the quasi-biennial oscillations (qbos), superposed on the scs. the qbos are thought to be a global phenomena extending from the subsurface layers of the sun to earth and throughout the heliosphere with a period generally between 1.3 and 1.6 years. in this study, we, for the first time, detected signals with periods ranging from 1.3 to 1.6 years in earth's magnetosphere, which can be associated with the solar qbos, using data from multiple goes missions. the qbo-like signals detected in earths magnetopshere are thought to be propagated via the solar wind from the solar surface. | detection of solar qbo-like signals in earth's magnetic field from multi-goes mission data |
helmod is a monte-carlo model that reproduce solar modulation process inside the heliosphere. the model include diffusion, particle drift, convection and adiabatic energy loss. the main time dependent parameters are solar observable like sunspot number, tilt angle of neutral current sheet, solar wind speed and interplanetary magnetic field measured at earth. the model includes both description of inner and outer heliosphere. outer boundary is evacuated with a time dependent procedure that agrees with insitu voyagers measurements. the long-term description of time dependent solar modulation was computed for proton and nuclei. furthermore, using historical records of such parameters, it is possible to estimate forecast of solar activity for solar cycle 25 and 26. present work will show the forecast procedure up to 22 years and accuracy of such predictions. | long term time dependent solar modulation using helmod monte-carlo model |
the paper presents the results of a joint analysis of the earth's main magnetic field (core field) bigrf and the large-scale magnetic field (lsmf) of the sun. selected 11- and 22-year periods of lsmf and bigrf variations are well manifested in both fields and are usually modulated by solar activity. even 11-year cycles for which the direction of the sun's magnetic field coincides with the direction of the earth's magnetic field are characterized by the minimum values of sunspot numbers, and odd cycles with opposite directions of magnetic fields have larger values of sunspot numbers. the rotation rate of two- and four-sector structure of the sun source of lsmf varied with about 11-year and 22-year cycle. longer changes in the magnetic fields of the sun and the earth with a period of about 75 years have also been revealed. the rotation periods of the sun source global field (28,0-28,5 days) were maximum at the middle of the 20th century in the period 1940÷1960 years. this maximum of solar activity corresponds to temporal gradient of geomagnetic field. it is shown that the gradient of the geomagnetic field bigrf depends on the rate of change in the length of the day. so, according to the results of the study, the rotation modes of the sun and the earth cause different periodic changes in their magnetic fields. | the earth's magnetic field and the large-scale magnetic field of the sun: the solar-terrestrial connection |
it is widely accepted that the variability of the solar white-light corona is closely connected to the solar activity. many previous studies have revealed that the temporal variation of the total radiance of the k-corona follows the solar cycle pattern (e.g., correlated with sunspot number). however, systematic studies on the origin of the coronal mass and its variability are still rare. in this study, by means of the spherically symmetric inversion (ssi) method we reconstruct 3d coronal densities for carrington rotations (crs) 2079--2180 over 2009--2017 using polarized brightness (pb) images observed with stereo/cor1 and lasco/c2. we calculate the total coronal mass from these density reconstructions within certain radial ranges, and compare its temporal evolution with the total magnetic flux measured from soho/mdi and sdo/hmi. we find a high correlation between the variations of total coronal mass and magnetic flux, and the former appears to be lagged by a cr to the latter during the rising phase of cycle 24. to confirm this finding we also compare the observed coronal masses with those calculated from global thermodynamic mhd models by predictive science inc (psi), and compare the evolution of sdo/eve line emissions between the chromosphere and the corona. in addition, we also explore the origin of the peaks in coronal mass and magnetic flux variations during the rising phase of cycle 24. | relationship between the coronal activity and magnetic flux over solar cycle 24 |
in the minimum of solar activity 2007–2008, there was an extremely long stable state of the structures of the solar wind speed, which persisted for 14 rotations of the sun. according to the neutron monitor (apatity), which registered galactic protons with energy > 500 mev, and the integral channel ep> 50 mev of the ephin, soho instrument, quasi-27-day variations in the fluxes of galactic protons were studied. periods of their variations turned out to coincide with the periods of the long-lived structures of the solar wind, 27.1 days, and anticorrelated with them. simultaneously periodic increases in the fluxes of jovian electrons (je >1 mev) were observed. at the beginning of the cycle of these variations, the fluxes of jovian electrons and galactic protons correlated, then, a small phase shift of correlation took place at each rotation of the sun, so that by the middle of the cycle already complete anticorrelation of these fluxes took place. this difference in the behavior of jovian electrons and galactic protons indicates the different nature of the observed quasi-27-day variations. while for galactic protons, the explanation is in modulation of charged particle fluxes by an interplanetary magnetic field associated with periodic variations in the solar wind, for jovian electrons, the relative position of the electron source (jupiter magnetosphere) and the earth and electron propagation process in jupiter-earth space must be took into account. | fluxes of jovian electrons and galactic protons in the minimum of 23-24 cycles of solar activity |
we model the sun's large-scale magnetic field and total solar irradiance (tsi) since 1700 by combining flux transport simulations with empirical relationships between facular brightening, sunspot darkening, and the total photospheric flux. the photospheric field is evolved subject to the constraints that (1) the flux emergence rate scales as the yearly sunspot numbers, and (2) the polar field strength at solar minimum is proportional to the amplitude of the following cycle. simulations are performed using both the recently revised sunspot numbers and an average of these numbers and the hoyt- schatten group numbers. a decrease (increase) in the polar field strength from one cycle to the next is simulated either by increasing (decreasing) the poleward flow speed, or by decreasing (increasing) the average axial tilts of active regions; the resulting photospheric field evolution is very similar whichever parameter is varied. comparisons between irradiance data and both the simulated and observed photospheric field suggest that tsi and facular brightness increase less steeply with the field strength at solar minimum than at other phases of the cycle, presumably because of the dominance of small- scale ephemeral regions when activity is very low. this relative insensitivity of the irradiance to changes in the large-scale field during cycle minima results in a minimum-to-minimum increase of annual tsi from 1700 to 1964 (2008) of 0.2(0.06)w/m2, a factor of 2-3 smaller than predicted in earlier reconstructions where the relation between facular brightness and field strength was assumed to be independent of cycle phase. (1 data file). | vizier online data catalog: reconstruction of solar irradiance from 1700 to 2019 (wang+, 2021) |
while limited solar radiation might hinder activation of volatiles in some distant icy bodies beyond the snowline, recent observations have shown that water and organic volatiles are prevalent throughout our solar system, including many previously unexpected locations like the asteroid belt (ceres) and several moons of the outer planets (e.g. europa, enceladus). these discoveries are leading to new strategies that aim better understanding (and confirmation) of key conditions that could permit habitability in ocean worlds, including the characterization of water environments and the search for plumes. while space-based assets, like galileo, cassini, and hubble space telescope (hst), have provided unique insight to plume activity, ground-based observations represent a unique and complementary effort that permit measurements of water molecules directly (not its by-products h and o), whose excitation mechanisms are less dependent of electron and/or magnetic environments. we aim to test plume activity, characterize europa's terrain, and provide sensitive upper limits of water vapor at different europan sub-longitudes. ultimately, these global results can strategically inform possible localized measurements with spacecraft missions like the james webb telescope (jwst), europa clipper, and juice, and complement studies that are currently underway with hst at uv wavelengths as part of hubble's mid-cycle 25 europa campaigns. thus far, we have been able to acquire observations of europa with keck/nirspec and irtf/ishell in 2016 and 2017, covering 60% of its surface (41 hr on-source). in this presentation we will discuss key aspects of our observing strategy, data analysis, and resulting sensitivities in the context of hst measurements. this work is supported by nasa's keck pi data award (pi l.p.) and solar system observation program (pi l.p.), and by the nasa astrobiology institute through funding awarded to the goddard center for astrobiology (pi m.j.m.). | measurements of plume activity on europa using ground-based infrared facilities |
this study presents the results of spectral observations of solar radiation in the uvb (280-315 nm) and uva (315-400 nm) range conducted at novolazarevskaya station (antarctica), polar station cape baranov (severnaya zemlya archipelago), and russian arctic scientific expedition on spitsbergen. the aim of these observations is to investigate the temporal characteristics of the uv radiation reaching the earth's surface during the 11-year solar activity cycle. control measurements of the uvb-uva intensity were conducted using avaspec-2048 (3648) fiber optic spectrometers on the solstice dates of december 21 between 2008 and 2019 in antarctica, as well as on june 22, 2019, in the arctic. the results indicate that the temporal range of the incoming uv radiation is formed by various mechanisms on the sun. regardless of the geographical location of the observation point, groups of oscillations with periods of 3-10 min and approximately 20 min are identified in all periodograms of the fourier analysis. these oscillations are identical to the harmonics of the frequency spectrum of solar oscillations in the range of 2-7 mhz. the periodograms of the near-surface atmospheric pressure (in hpa) at novolazarevskaya weather station reveal the presence of the same periods. based on seasonal observations conducted on severnaya zemlya archipelago between march 1, 2019 and august 31, 2019, we have identified a correlation between the solar radiation intensity in the nuv range (297-330 nm) and the magnitude of the full vector of the earth's magnetic field (f). the changes in f are known to be closely related to the mean magnetic field of the sun. it is concluded that the uvb-uva radiation, as well as solar oscillations and the mean magnetic field of the sun, affect the temporal characteristics of parameters in the lower atmosphere, from minutes to the hale cycle (~22 years). in the conclusions, a diagram illustrating the relationship between meteorological parameters in the near-surface layer of the atmosphere and the influx of uvb-uva radiation is presented. | the temporal characteristics of the uvb-uva solar radiation during seasonal observation periods in antarctica and the arctic |
detailed knowledge of the magnetic and thermal environment of the solar atmosphere, including the photosphere, chromsosphere, and the corona, is crucial for the understanding of the physics of solar eruptions. recent progresses in spectropolarimetric measurements of magnetically sensitive emission lines provides a viable path towards quantitative characterization of the three-dimensional (3d) structure of coronal magnetic fields - the main driver of coronal phenomena. however, the inference of the 3d coronal vector magnetic fields from observations is not straightforward due to the complex nature of the emission process (resonance scattering through hanle and zeeman effects) and line-of-sight (los) integration through the optically thin corona. the latter can be resolved by employing tomographic inversion technique using observations from multiple sight lines. in a recent work (kramar et al., 2016), we have applied vector tomography method to the coronal emission line (cel) linear polarization data (i, q, and u maps) obtained by coronal multichannel polarimeter (comp) to derive 3d coronal magnetic fields revealing coronal structures (streamers, pseudostreamers, coronal holes) to demonstrate the feasibility of the methods. although linear polarization tomography can be used to probe certain coronal field configuration (kramar et al. 2013), linear polarization data alone does not allow us to uniquely reconstruct all possible field configurations in general. vector tomography of coronal magnetic field is currently limited to linear polarization tomography due to the difficulty of circular polarization observations. however, with the pending completion of the daniel k. inouye solar telescope and the 2020 launch of india's aditya mission aimed to provide full-stokes cel polarization measurements on a routine basis, the full-stokes vector tomography of coronal magnetic fields will be possible in the near future. we will discuss how inclusion of circular polarization data will improve the accuracy of magnetic field reconstruction, and present new research on the 3d reconstructions of the coronal vector magnetic fields using the full polarization spectra (i, q, u, and v) of coronal emission lines. | retrieving 3d coronal magnetic field from spectropolarimetry of coronal emission lines. |
homogeneous observations of the magnetic fields on the solar photosphere are invaluable for understanding the solar dynamics at long (11-year solar cycle) and short (solar flares and eruptions) timescales. the operational periods of the solar dynamics observatory/helioseismic and magnetic imager (sdo/hmi) and the solar and heliospheric observatory/michelson doppler imager (soho/mdi) collectively span over 25 years since 1996. while these observations cover more than two solar cycles, the instruments have different spatial resolutions, locations, and spectral lines for magnetic field estimation, which generates differences in their magnetograms. we aim to develop a homogeneous solar magnetic data set for active regions by regressing sdo/hmi magnetograms to soho/mdi-like magnetograms. the magnetograms of 81 solar active regions simultaneously covered by sdo/hmi and soho/mdi over the period of may 2010 - april 2011 were remapped and aligned for temporal overlap. machine learning models were used to generate soho/mdi-like magnetograms from sdo/hmi magnetograms depending on active region location and spacecraft radial velocity. we evaluate and present our results for pixel-to-pixel regression algorithms, as well as discuss the application of image-to-pixel algorithms for magnetogram homogenization. | cross-calibration of magnetic field measurements of solar active regions |
the empirical model of high-latitude boundary of the outer radiation belt has been updated on the base of leo satellite measurements of energetic electron fluxes obtained during long time period, larger than one solar cycle (2005-2017). the model was corrected taking into account internal magnetic field secular variations and corresponding magnetic poles movement during the observation period. analytical equation for the high-latitude boundary of the trapped 100 kev energetic electrons was obtained in dependence on ut, energy and geomagnetic activity level. forecasting capability of the model was realized in the framework of msu's space monitoring data center using the forecast of the dst index. automatic boundary detection method was developed based on leo satellite measurements of charged particle fluxes for different energetic channels and at different altitudes. the experimentally obtained position of high-latitude boundary of the outer radiation belt was compared with the results of model calculations. | energetic dependences of high latitude boundary of the outer radiation belt as measured by russian leo satellites in 2005-2017 |
in this paper, the statistical features of scintillations and cycle slips of gps (global positioning system) signals, as well as the effects of solar activity and geomagnetic activity on scintillations and cycle slips have been analyzed and compared by means of the observations from a scintillation observation network in the mid-south region of china during 2012-2015. results show that the statistical features of scintillations and cycle slips. the results show that the variation features of cycle slip occurrence with local time, month, solar activity and geomagnetic activity are very similar to those of scintillation occurrence, and the occurring probability of cycle slip increases as the s4 index increases, suggesting that cycle slips are closely related to scintillations and scintillations are a key factor which can cause cycle slips. scintillations and cycle slips occur mainly during the night, most frequently before midnight and seldom in the daytime. it is found that scintillations and cycle slips occur mainly in equinox months but seldom in solstice months at the ionization anomaly crest and its adjacent regions, and an equinoctial asymmetry that scintillations and cycle slips occur more frequently in spring than in autumn is also found. the occurrence of scintillations and cycle slips shows a strong dependence on the solar activity, it increases as the solar activity increases. however, the occurrence of scintillations and cycle slips shows a negative correlation with geomagnetic activity. the geomagnetic disturbances inhibit scintillations and cycle slips as a whole. on average, the closer to the magnetic equator, the more frequently and the earlier scintillations occur, indicating that the scintillations are caused by ionospheric irregularities which originate at the magnetic equator. in addition, there is a good consistency between the spatial distributions of scintillations and cycle slips. they mainly occur in the area with elevation angle between 35° and 55° and azimuth angle between 150° and 240°. | a comparison of statistical features of ionospheric scintillations and cycle slips in the mid-south region of china |
magnetic bright points (mbps) are small-scale, very strong, solar magnetic field concentrations visible in the lower solar atmosphere. while there is a large and ever-increasing knowledge base and understanding of large-scale solar magnetic fields, i.e., sunspots and active regions, and their involvement in the solar cycle, much less is known about small-scale fields such as mbps. thus, we aim on contributing to our understanding of these tiny, but, important solar features by investigating the size distribution and its variation over time. for this purpose, we obtained the synoptic g-band data set of the hinode mission which is now since nearly 12 years in space and operational (launched in october 2006). after careful image calibration and selection we analysed the g-band data set with an automated mbp identification algorithm to calculate in a next step the equivalent diameter of the mbps. the so gained size distribution follows a gamma distribution with pronounced changes during the solar activity cycle. the mbp sizes appear to be somewhat smaller during the solar minimum and somewhat more extended during the solar maxima as expressed by the scaleparameter of the gamma distribution. | long-term trends of magnetic bright points: the evolution of mbp size |
we use alma observations of co(2-1) in 13 massive (m * ≳ 1011 m ⊙) poststarburst galaxies at z ~ 0.6 to constrain the molecular gas content in galaxies shortly after they quench their major star-forming episode. the poststarburst galaxies in this study are selected from the sloan digital sky survey spectroscopic samples (data release 14) based on their spectral shapes, as part of the studying quenching at intermediate-z galaxies: gas, angu $\overrightarrow{l}\mathrm{ar}$ momentum, and evolution ( ${squigg}\vec{l}e$ ) program. early results showed that two poststarburst galaxies host large h2 reservoirs despite their low inferred star formation rates (sfrs). here we expand this analysis to a larger statistical sample of 13 galaxies. six of the primary targets (45%) are detected, with ${m}_{{{\rm{h}}}_{2}}\gtrsim {10}^{9}$ m ⊙. given their high stellar masses, this mass limit corresponds to an average gas fraction of $\langle {f}_{{{\rm{h}}}_{2}}\equiv {m}_{{{\rm{h}}}_{2}}/{m}_{* }\rangle \sim 7 \% $ or ~14% using lower stellar masses estimates derived from analytic, exponentially declining star formation histories. the gas fraction correlates with the dn 4000 spectral index, suggesting that the cold gas reservoirs decrease with time since burst, as found in local k+a galaxies. star formation histories derived from flexible stellar population synthesis modeling support this empirical finding: galaxies that quenched ≲150 myr prior to observation host detectable co(2-1) emission, while older poststarburst galaxies are undetected. the large h2 reservoirs and low sfrs in the sample imply that the quenching of star formation precedes the disappearance of the cold gas reservoirs. however, within the following 100-200 myr, the ${squigg}\vec{l}e$ galaxies require the additional and efficient heating or removal of cold gas to bring their low sfrs in line with standard h2 scaling relations. | now you see it, now you don't: star formation truncation precedes the loss of molecular gas by 100 myr in massive poststarburst galaxies at z 0.6 |
this paper presents the mass assembly time scales of nearby galaxies observed by califa at the 3.5 m telescope in calar alto. we apply the fossil record method of the stellar populations to the complete sample of the 3rd califa data release, with a total of 661 galaxies, covering stellar masses from 108.4 to 1012m⊙ and a wide range of hubble types. we apply spectral synthesis techniques to the datacubes and process the results to produce the mass growth time scales and mass weighted ages, from which we obtain temporal and spatially resolved information in seven bins of galaxy morphology (e, s0, sa, sb, sc, and sd) and six bins of stellar mass and stellar mass surface density. we use three different tracers of the spatially resolved star formation history (mass assembly curves, ratio of half mass to half light radii, and mass-weighted age gradients) to test if galaxies grow inside-out, and its dependence with galaxy stellar mass, stellar mass surface density, and morphology. our main results are as follows: (a) the innermost regions of galaxies assemble their mass at an earlier time than regions located in the outer parts; this happens at any given stellar mass (m⋆), stellar mass surface density (σ⋆), or hubble type, including the lowest mass systems in our sample. (b) galaxies present a significant diversity in their characteristic formation epochs for lower-mass systems. this diversity shows a strong dependence of the mass assembly time scales on σ⋆ and hubble type in the lower-mass range (108.4 to 1010.4), but a very mild dependence in higher-mass bins. (c) the lowest half mass radius (hmr) to half light radius (hlr) ratio is found for galaxies between 1010.4 and 1011.1m⊙, where galaxies are 25% smaller in mass than in light. low-mass galaxies show the largest ratio with hmr/hlr 0.89. sb and sbc galaxies present the lowest hmr/hlr ratio (0.74). the ratio hmr/hlr is always, on average, below 1, indicating that galaxies grow faster in mass than in light. (d) all galaxies show negative ⟨log age⟩ m gradients in the inner 1 hlr. the profile flattens (slope less negative) with increasing values of σ⋆. there is no significant dependence on m⋆ within a particular σ⋆ bin, except for the lowest bin, where the gradients becomes steeper. (e) downsizing is spatially preserved as a function of m⋆ and σ⋆, but it is broken for e and so where the outer parts are assembled in later epochs than sa galaxies. these results suggest that independently of their stellar mass, stellar mass surface density, and morphology, galaxies form inside-out on average. | the spatially resolved star formation history of califa galaxies. cosmic time scales |
we perform jeans anisotropic modeling (jam) on elliptical and spiral galaxies from the manga dr13 sample. by comparing the stellar mass-to-light ratios estimated from stellar population synthesis and from jam, we find a systematic variation of the initial mass function (imf) similar to that in the earlier {atlas}}3{{d}} results. early-type galaxies (elliptical and lenticular) with lower velocity dispersions within one effective radius are consistent with a chabrier-like imf, while galaxies with higher velocity dispersions are consistent with a more bottom-heavy imf such as the salpeter imf. spiral galaxies have similar systematic imf variations, but with slightly different slopes and larger scatters, due to the uncertainties caused by the higher gas fractions and extinctions for these galaxies. furthermore, we examine the effects of stellar mass-to-light ratio gradients on our jam modeling, and we find that the trends become stronger after considering the gradients. | sdss-iv manga: variation of the stellar initial mass function in spiral and early-type galaxies |
the source of energetic photons that heated and reionized the early universe remains uncertain. early galaxies had low metallicity and recent population synthesis calculations suggest that the number and luminosity of high-mass x-ray binaries are enhanced in star-forming galaxies with low metallicity, offering a potentially important and previously overlooked source of heating and reionization. lyman break analogue (lba) galaxies are local galaxies that strongly resemble the high-redshift, star-forming lyman break galaxies and have been suggested as local analogues to these metal-deficient galaxies found in the early universe. we studied a sample of 10 lbas in order to measure the relation between star formation rate and x-ray luminosity. we found that for lbas with metallicities in the range 12 + log10(o/h) = 8.15-8.80, the lx -sfr relation was log _{10} (l_x/sfr {[erg s^{-1} m_{⊙}^{-1} yr]}) = 39.85(± 0.10) in the 0.5-8 kev band with a dispersion of σ = 0.25 dex. this is an enhancement of nearly a factor of 2 in the l0.5-8 kev-sfr relation relative to results for nearby, near-solar metallicity galaxies. the enhancement is significant at the 98.2 per cent level (2.4σ). our enhanced lx/sfr relation is consistent with the metallicity-dependent predicted value from population synthesis models. we discuss the possibility of an lx-sfr-metallicity plane for star-forming galaxies. these results are important to our understanding of reionization and the formation of early galaxies. | enhanced x-ray emission from lyman break analogues and a possible lx-sfr-metallicity plane |
using our population synthesis code, we found that the typical chirp mass defined by (m1m2)3/5/(m1 + m2)1/5 of population iii (pop iii) binary black holes (bh-bhs) is ∼30 m⊙ with the total mass of ∼60 m⊙ so that the inspiral chirp signal as well as quasi-normal mode (qnm) of the merging black hole (bh) are interesting targets of kagra. the detection rate of the coalescing pop iii bh-bhs is ∼180 events yr- 1 (sfrp/(10-2.5 m⊙ yr-1 mpc-3))([fb/(1 + fb)]/0.33)errsys in our standard model, where sfrp, fb and errsys are the peak value of the pop iii star formation rate, the binary fraction and the systematic error with errsys = 1 for our standard model, respectively. to evaluate the robustness of chirp mass distribution and the range of errsys, we examine the dependence of the results on the unknown parameters and the distribution functions in the population synthesis code. we found that the chirp mass has a peak at ∼30 m⊙ in most of parameters and distribution functions as well as errsys ranges from 0.046 to 4. therefore, the detection rate of the coalescing pop iii bh-bhs ranges about 8.3-720 events yr- 1(sfrp/(10- 2.5 m⊙ yr- 1 mpc- 3))([fb/(1 + fb)]/0.33). the minimum rate corresponds to the worst model which we think unlikely so that unless (sfrp/(10- 2.5 m⊙ yr- 1 mpc- 3))([fb/(1 + fb)]/0.33) ≪ 0.1, we expect the pop iii bh-bhs merger rate of at least one event per year by kagra. nakano, tanaka & nakamura show that if signal-to-noise ratio (s/n) of qnm is larger than 35, we can confirm or refute the general relativity (gr) more than 5σ level. in our standard model, the detection rate of pop iii bh-bhs whose s/n is larger than 35 is 3.2 events yr- 1 (sfrp/(10- 2.5 m⊙ yr- 1 mpc- 3))([fb/(1 + fb)]/0.33)errsys. thus, there is a good chance to check whether gr is correct or not in the strong gravity region. | the detection rate of inspiral and quasi-normal modes of population iii binary black holes which can confirm or refute the general relativity in the strong gravity region |
we present speculator -- a fast, accurate, and flexible framework for emulating stellar population synthesis (sps) models for predicting galaxy spectra and photometry. for emulating spectra, we use a principal component analysis to construct a set of basis functions and neural networks to learn the basis coefficients as a function of the sps model parameters. for photometry, we parameterize the magnitudes (for the filters of interest) as a function of sps parameters by a neural network. the resulting emulators are able to predict spectra and photometry under both simple and complicated sps model parameterizations to percent-level accuracy, giving a factor of 103-104 speedup over direct sps computation. they have readily computable derivatives, making them amenable to gradient-based inference and optimization methods. the emulators are also straightforward to call from a gpu, giving an additional order of magnitude speedup. rapid sps computations delivered by emulation offers a massive reduction in the computational resources required to infer the physical properties of galaxies from observed spectra or photometry and simulate galaxy populations under sps models, while maintaining the accuracy required for a range of applications. | speculator: emulating stellar population synthesis for fast and accurate galaxy spectra and photometry |
we use the rapid binary population synthesis code compas to investigate commonly used prescriptions for the determination of mass transfer stability in close binaries and the orbital separations after stable mass transfer. the degree of orbital tightening during nonconservative mass transfer episodes is governed by the poorly constrained angular momentum carried away by the ejected material. increased orbital tightening drives systems toward unstable mass transfer leading to a common envelope. we find that the fraction of interacting binaries that will undergo only stable mass transfer throughout their lives fluctuates between a few and ~20% due to uncertainty in the angular momentum loss alone. if mass transfer is significantly nonconservative, stability prescriptions that rely on the assumption of conservative mass transfer underpredict the number of systems which experience unstable mass transfer and stellar mergers. this may substantially impact predictions about the rates of various transients, including luminous red novae, stripped-envelope supernovae, x-ray binaries, and the progenitors of coalescing compact binaries. | the impact of angular momentum loss on the outcomes of binary mass transfer |
the manga project has obtained integral field unit (ifu) data for several thousand nearby galaxies, including barred galaxies. with the two-dimensional spectral and kinematic information provided by ifus, we can measure the pattern speed of a barred galaxy, which determines the bar dynamics. we apply the non-parametric method proposed by tremaine & weinberg to estimate the bar pattern speed for 53 barred galaxies, making this the largest sample studied so far in this way. our sample is selected from the manga first public data release as part of sdss data release 13 according mainly to the axial ratio and position angle difference between the bar and disc, while kinematic data are from the later sdss data release 14. we have used both the photometric position angle from the photometric image and the kinematic position angle from the stellar velocity map to derive the pattern speed. combining three independent bar length measurements and the circular velocity from jeans anisotropic modelling (jam), we also determine the dimensionless ratio r of the corotation radius to the bar length. we find that the galaxy's position angle is the main uncertainty in determining the bar pattern speed. the kinematic position angle leads to fewer ultrafast bars than the photometric position angle, and this could be due to the method of measuring the kinematic position angle. we study the dependence of r values on galaxy properties such as the dark matter fraction from jam modelling and the stellar age and metallicity from stellar population synthesis. a positive correlation between the bar length and bar strength is found: the longer the bar, the stronger the bar. however, no other significant correlations are found. this may result from errors in deriving the r values or from the complex formation and slowdown processes of galactic bars. | sdss-iv manga: pattern speeds of barred galaxies |
using new long-slit spectroscopy obtained with x-shooter at eso-vlt, we study, for the first time, radial gradients of optical and near-infrared initial mass function (imf)-sensitive features in a representative sample of galaxies at the very high mass end of the galaxy population. the sample consists of seven early-type galaxies (etgs) at z ∼ 0.05, with central velocity dispersion in the range 300 ≲ σ ≲ 350 km s-1. using state-of-the-art stellar population synthesis models, we fit a number of spectral indices, from different chemical species (including tio and na indices), to constrain the imf slope (i.e. the fraction of low-mass stars), as a function of galactocentric distance, over a radial range out to ∼4 kpc. etgs in our sample show a significant correlation of imf slope and surface mass density. the bottom-heavy population (i.e. an excess of low-mass stars in the imf) is confined to central galaxy regions with surface mass density above ∼ 10^{10} m_⊙ kpc^{-2}, or, alternatively, within a characteristic radius of ∼2 kpc. radial distance, in physical units, and surface mass density are the best correlators to imf variations, with respect to other dynamical (e.g. velocity dispersion) and stellar population (e.g. metallicity) properties. our results for the most massive galaxies suggest that there is no single parameter that fully explains variations in the stellar imf, but imf radial profiles at z ∼ 0 rather result from the complex formation and mass accretion history of galaxy inner and outer regions. | imf radial gradients in most massive early-type galaxies |
we estimate ages, metallicities, α-element abundance ratios, and stellar initial mass functions (imfs) of elliptical (e) and s0 galaxies from the manga-dr15 survey. we stack spectra and use a variety of single stellar population synthesis models to interpret the absorption line strengths in these spectra. we quantify how these properties vary across the population, as well as with galactocentric distance. this paper is the first of a series and is based on a sample of pure elliptical galaxies at z ≤ 0.08. we confirm previous work showing that imfs in es with the largest luminosity (lr) and central velocity dispersion (σ0) appear to be increasingly bottom heavy towards their centres. for these galaxies the stellar mass-to-light ratio decreases at most by a factor of 2 from the central regions to re. in contrast, for lower lr and σ0 galaxies, the imf is shallower and m*/lr in the central regions is similar to the outskirts, although quantitative estimates depend on assumptions about element abundance gradients. accounting self-consistently for these gradients when estimating both m* and mdyn brings the two into good agreement: gradients reduce mdyn by ∼0.2 dex while only slightly increasing the m* inferred using a kroupa imf. this is a different resolution of the m*-mdyn discrepancy than has been followed in the recent literature where m* of massive galaxies is increased by adopting a salpeter imf throughout the galaxy while leaving mdyn unchanged. a companion paper discusses how stellar population differences are even more pronounced if one separates slow from fast rotators. | galaxy properties as revealed by manga - i. constraints on imf and m*/l gradients in ellipticals |
aims: we attempt to constrain the kinematics of the thin and thick disks using the besançon population synthesis model together with rave dr4 and gaia first data release (tgas).methods: the rave fields were simulated by applying a detailed target selection function and the kinematics was computed using velocity ellipsoids depending on age in order to study the secular evolution. we accounted for the asymmetric drift computed from fitting a stäckel potential to orbits. model parameters such as velocity dispersions, mean motions, and velocity gradients were adjusted using an abc-mcmc method. we made use of the metallicity to enhance the separation between thin and thick disks.results: we show that this model is able to reproduce the kinematics of the local disks in great detail. the disk follows the expected secular evolution, in very good agreement with previous studies of the thin disk. the new asymmetric drift formula, fitted to our previously described stäckel potential, fairly well reproduces the velocity distribution in a wide solar neighborhood. the u and w components of the solar motion determined with this method agree well with previous studies. however, we find a smaller v component than previously thought, essentially because we include the variation of the asymmetric drift with distance to the plane. the thick disk is represented by a long period of formation (at least 2 gyr), during which, as we show, the mean velocity increases with time while the scale height and scale length decrease, very consistently with a collapse phase with conservation of angular momentum.conclusions: this new galactic dynamical model is able to reproduce the observed velocities in a wide solar neighborhood at the quality level of the tgas-rave sample, allowing us to constrain the thin and thick disk dynamical evolution, as well as determining the solar motion. | kinematics of the local disk from the rave survey and the gaia first data release |
we present spectra of five ultra-diffuse galaxies (udgs) in the vicinity of the coma cluster obtained with the multi-object double spectrograph on the large binocular telescope. we confirm four of these as members of the cluster, quintupling the number of spectroscopically confirmed systems. like the previously confirmed large (projected half-light radius >4.6 kpc) udg, df44, the systems we targeted all have projected half-light radii > 2.9 {kpc}. as such, we spectroscopically confirm a population of physically large udgs in the coma cluster. the remaining udg is located in the field, about 45 mpc behind the cluster. we observe balmer and ca ii h and k absorption lines in all of our udg spectra. by comparing the stacked udg spectrum against stellar population synthesis models, we conclude that, on average, these udgs are composed of metal-poor stars ([fe/h] ≲ -1.5). we also discover the first udg with [o ii] and [o iii] emission lines within a clustered environment, demonstrating that not all cluster udgs are devoid of gas and sources of ionizing radiation. | spectroscopy of ultra-diffuse galaxies in the coma cluster |
dedicated photometric and spectroscopic surveys have provided unambiguous evidence for a strong stellar mass-size evolution of galaxies within the last 10 gyr. the likely progenitors of today's most massive galaxies are remarkably small, discy, passive and have already assembled much of their stellar mass at redshift z = 2. an in-depth analysis of these objects, however, is currently not feasible due to the lack of high-quality, spatially resolved photometric and spectroscopic data. in this paper, we present a sample of nearby compact elliptical galaxies (cegs), which bear resemblance to the massive and quiescent galaxy population at earlier times. hubble space telescope (hst) and wide-field integral field unit (ifu) data have been obtained, and are used to constrain orbit-based dynamical models and stellar population synthesis (sps) fits, to unravel their structural and dynamical properties. we first show that our galaxies are outliers in the present-day stellar mass-size relation. they are, however, consistent with the mass-size relation of compact, massive and quiescent galaxies at redshift z = 2. the compact sizes of our nearby galaxies imply high central stellar mass surface densities, which are also in agreement with the massive galaxy population at higher redshift, hinting at strong dissipational processes during their formation. corroborating evidence for a largely passive evolution within the last 10 gyr is provided by their orbital distribution as well as their stellar populations, which are difficult to reconcile with a very active (major) merging history. this all supports that we can use nearby cegs as local analogues of the high-redshift, massive and quiescent galaxy population, thus providing additional constraints for models of galaxy formation and evolution. | the structural and dynamical properties of compact elliptical galaxies |
minijpas is a ∼1 deg2 imaging survey of the aegis field in 60 bands, performed to demonstrate the scientific potential of the upcoming javalambre-physics of the accelerating universe astrophysical survey (j-pas). full coverage of the 3800-9100 å range with 54 narrow-band filters, in combination with 6 optical broad-band filters, allows for extremely accurate photometric redshifts (photo-z), which, applied over areas of thousands of square degrees, will enable new applications of the photo-z technique, such as measurement of baryonic acoustic oscillations. in this paper we describe the method we used to obtain the photo-z that is included in the publicly available minijpas catalogue, and characterise the photo-z performance. we built photo-spectra with 100 å resolution based on forced-aperture photometry corrected for point spread function. systematic offsets in the photometry were corrected by applying magnitude shifts obtained through iterative fitting with stellar population synthesis models. we computed photo-z with a customised version of lephare, using a set of templates that is optimised for the j-pas filter-set. we analysed the accuracy of minijpas photo-z and their dependence on multiple quantities using a subsample of 5266 galaxies with spectroscopic redshifts from sdss and deep, which we find to be representative of the whole r < 23 minijpas sample. formal 1σ uncertainties for the photo-z that are calculated with the δχ2 method underestimate the actual redshift errors. the odds parameter has a stronger correlation with |δz| and accurately reproduces the probability of a redshift outlier (|δz| > 0.03), regardless of the magnitude, redshift, or spectral type of the sources. we show that the two main summary statistics characterising the photo-z accuracy for a population of galaxies (σnmad and η) can be predicted by the distribution of odds in this population, and we use this to estimate the statistics for the whole minijpas sample. at r < 23, there are ∼17 500 galaxies per deg2 with valid photo-z estimates, ∼4200 of which are expected to have |δz| < 0.003. the typical error is σnmad = 0.013 with an outlier rate η = 0.39. the target photo-z accuracy σnmad = 0.003 is achieved for odds > 0.82 with η = 0.05, at the cost of decreasing the density of selected galaxies to n ∼ 5200 deg−2 (∼2600 of which have |δz| < 0.003). | the minijpas survey: photometric redshift catalogue |
suppression of h2-cooling in early protogalaxies has important implications for the formation of supermassive black hole seeds, the first generation of stars and the epoch of reionization. this suppression can occur via photodissociation of h2 (by ultraviolet lyman-werner [lw] photons) or by photodetachment of h-, a precursor in h2 formation (by infrared [ir] photons). previous studies have typically adopted idealized spectra, with a blackbody or a power-law shape, in modelling the chemistry of metal-free protogalaxies, and utilized a single parameter, the critical uv flux, or jcrit, to determine whether h2-cooling is prevented. this can be misleading, as independent of the spectral shape, there is a critical curve in the (k_lw,k_h^-) plane, where klw and k_h^- are the h2-dissocation rates by lw and ir photons, which determines whether a protogalaxy can cool below ∼1000 k. we use a one-zone model to follow the chemical and thermal evolution of gravitationally collapsing protogalactic gas, to compute this critical curve and provide an accurate analytical fit for it. we improve on previous works by considering a variety of more realistic pop iii or pop ii-type spectra from population synthesis models and perform fully frequency-dependent calculations of the h2-photodissociation rates for each spectrum. we compute the ratio k_lw/k_h^- for each spectrum, as well as the minimum stellar mass m*, for various imfs and metallicities, required to prevent cooling in a neighbouring halo a distance d away. we provide critical m*/d2 values for suppression of h2-cooling, with analytic fits, which can be used in future studies. | beyond jcrit: a critical curve for suppression of h2-cooling in protogalaxies |
we perform a detailed study of the cosmological bias of gravitational gave (gw) events produced by binary black hole mergers (bbhm). we start from a bbhm distribution modeled inside the eagle hydrodyamical simulation using the population synthesis code mobse. we then compare our findings with predictions from different halo occupation distribution (hod) prescriptions and find overall agreement, provided that the modeled properties of host galaxies and halos in the semi-analytical treatment match those in the simulations. by highlighting the sources of these discrepancies, we provide the stepping stone to build future more robust models that prevent the shortcoming of both simulation-based and analytical models. finally, we train a neural network to build a simulation-based hod and perform feature importance analysis to gain intuition on which host halo/galaxy parameters are the most relevant in determining the actual distribution and power spectrum of bbhm. we find that the distribution of bbhm in a galaxy does not only depend on its size, star formation rate and metallicity, but also by its kinetic state. | clustering of binary black hole mergers: a detailed analysis of the eagle+mobse simulation |
the formation and evolution of local brightest cluster galaxies (bcgs) is investigated by determining the stellar populations and dynamics from the galaxy core, through the outskirts and into the intracluster light (icl). integral spectroscopy of 23 bcgs observed out to 4 re is collected and high signal-to-noise regions are identified. stellar population synthesis codes are used to determine the age, metallicity, velocity, and velocity dispersion of stars within each region. the icl spectra are best modelled with populations that are younger and less metal-rich than those of the bcg cores. the average bcg core age of the sample is 13.3± 2.8 gyr and the average metallicity is [fe/h] = 0.30± 0.09, whereas for the icl the average age is 9.2± 3.5 gyr and the average metallicity is [fe/h] = 0.18± 0.16. the velocity dispersion profile is seen to be rising or flat in most of the sample (17/23), and those with rising values reach the value of the host cluster's velocity dispersion in several cases. the most extended bcgs are closest to the peak of the cluster's x-ray luminosity. the results are consistent with the idea that the bcg cores and inner regions formed quickly and long ago, with the outer regions and icl forming more recently, and continuing to assemble through minor merging. any recent star formation in the bcgs is a minor component, and is associated with the cluster cool core status. | clocking the formation of today's largest galaxies: wide field integral spectroscopy of brightest cluster galaxies and their surroundings |
the calar alto legacy integral field area (califa) survey, a pioneer in integral field spectroscopy legacy projects, has fostered many studies exploring the information encoded on the spatially resolved data on gaseous and stellar features in the optical range of galaxies. we describe a value-added catalogue of stellar population properties for califa galaxies analysed with the spectral synthesis code starlight and processed with the pycasso platform. our public database (http://pycasso.ufsc.br/, mirror at http://pycasso.iaa.es/) comprises 445 galaxies from the califa data release 3 with combo data. the catalogue provides maps for the stellar mass surface density, mean stellar ages and metallicities, stellar dust attenuation, star formation rates, and kinematics. example applications both for individual galaxies and for statistical studies are presented to illustrate the power of this data set. we revisit and update a few of our own results on mass density radial profiles and on the local mass-metallicity relation. we also show how to employ the catalogue for new investigations, and show a pseudo schmidt-kennicutt relation entirely made with information extracted from the stellar continuum. combinations to other databases are also illustrated. among other results, we find a very good agreement between star formation rate surface densities derived from the stellar continuum and the h α emission. this public catalogue joins the scientific community's effort towards transparency and reproducibility, and will be useful for researchers focusing on (or complementing their studies with) stellar properties of califa galaxies. | the pycasso database: spatially resolved stellar population properties for califa galaxies |
the origin of the spins of stellar-mass black holes is still controversial, and angular momentum transport inside massive stars is one of the main sources of uncertainty. here, we apply hierarchical bayesian inference to derive constraints on spin models from the 59 most confident binary black hole merger events in the third gravitational-wave transient catalogue (gwtc-3). we consider up to five parameters: chirp mass, mass ratio, redshift, effective spin, and precessing spin. for the model selection, we use a set of binary population synthesis simulations spanning drastically different assumptions for black hole spins and natal kicks. in particular, our spin models range from the maximal to minimal efficiency of angular momentum transport in stars. we find that if we include the precessing spin parameter into our analysis, models predicting only vanishingly small spins are in tension with gwtc-3 data. on the other hand, models in which most spins are vanishingly small but that also include a subpopulation of tidally spun-up black holes are a good match to the data. our results show that the precessing spin parameter has a crucial impact on model selection. | binary black hole spins: model selection with gwtc-3 |
unlike newtonian dynamics which is linear and obeys the strong equivalence principle, in any non-linear gravitation such as milgromian dynamics (mond), the strong version of the equivalence principle is violated and the gravitational dynamics of a system is influenced by the external gravitational field in which it is embedded. this so called external field effect (efe) is one of the important implications of mond and provides a special context to test milgromian dynamics. here, we study the rotation curves (rcs) of 18 spiral galaxies and find that their shapes constrain the efe. we show that the efe can successfully remedy the overestimation of rotation velocities in 80 per cent of the sample galaxies in milgromian dynamics fits by decreasing the velocity in the outer part of the rcs. we compare the implied external field with the gravitational field for non-negligible nearby sources of each individual galaxy and find that in many cases it is compatible with the efe within the uncertainties. we therefore argue that in the framework of milgromian dynamics, one can constrain the gravitational field induced from the environment of galaxies using their rcs. we finally show that taking into account the efe yields more realistic values for the stellar mass-to-light ratio in terms of stellar population synthesis than the ones implied without the efe. | declining rotation curves of galaxies as a test of gravitational theory |
we analyze the distribution of rest-frame u - v and v - j colors for star-forming galaxies at 0.5 < z < 2.5. using stellar population synthesis, stochastic star formation histories, and a simple prescription for the dust attenuation that accounts for the shape and inclination of galaxies, we construct a model for the distribution of galaxy colors. with only two free parameters, this model is able to reproduce the observed galaxy colors as a function of redshift and stellar mass remarkably well. our analysis suggests that the wide range of dust attenuation values measured for star-forming galaxies at a given redshift and stellar mass is almost entirely due to the effect of inclination; if all galaxies at a given stellar mass were observed edge-on, they would show very similar dust attenuation. this result has important implications for the interpretation of dust attenuation measurements, the treatment of uv and ir luminosity, and the comparison between numerical simulations and observations. | reproducing the uvj color distribution of star-forming galaxies at 0.5 < z < 2.5 with a geometric model of dust attenuation |
we present results of a supernova lightcurve population synthesis, predicting the range of possible supernova lightcurves arising from a population of progenitor stars that include interacting binary systems. we show that the known diversity of supernova lightcurves can be interpreted as arising from binary interactions. given detailed models of the progenitor stars, we are able to the determine what parameters within these stars determine the shape of their supernova lightcurve. the primary factors are the mass of supernova ejecta and the mass of hydrogen in the final progenitor. we find that there is a continuum of lightcurve behaviour from type iip, iil, to iib supernovae related to the range of hydrogen and ejecta masses. most type iib supernovae arise from a relatively narrow range of initial masses from 10 to 15 m⊙. we also find a few distinct lightcurves that are the result of stellar mergers. | supernova lightcurve population synthesis i: including interacting binaries is key to understanding the diversity of type ii supernova lightcurves |
we report the discovery and follow-up observations of a system of three objects identified by the alfalfa extragalactic hi survey, cataloged as (almost) dark extragalactic sources, i.e., extragalactic hi detections with no discernible counterpart in publicly available, wide-field, imaging surveys. we have obtained deep optical imaging with wiyn podi and hi synthesis maps with wsrt of the hi1232+20 system. the source with the highest hi flux has a newly discovered ultra-low surface brightness (lsb) optical counterpart associated with it, while the other two sources have no detected optical counterparts in our images. our optical observations show that the detected lsb optical counterpart has a peak surface brightness of ∼26.4 mag arcsec-2 in g‧, which is exceptionally faint. this source (agc 229385) has the largest accurately measured hi mass-to-light ratio of an isolated object: {{m}hi}/{{l}{{g\prime }}} = 46 {{m}⊙ }/{{l}⊙ }, and has an hi mass of 7.2 × {{10}8} {{m}⊙ }. the other two hi sources (with hi masses 2.0 × 108 and 1.2 × {{10}8} {{m}⊙ }) without optical counterparts have upper limit surface brightnesses of 27.9 and 27.8 mag arcsec-2 in g‧, and lower limits on their gas mass-to-light ratio of {{m}hi}/{{l}{{g\prime }}} > 57 and > 31 {{m}⊙ }/{{l}⊙ }. this system lies relatively close in projection to the virgo cluster, but velocity flow models indicate that it is located at 25 mpc, substantially beyond virgo. the system appears to be quite isolated, with no known object closer than ∼500 kpc. these hi sources may represent both sides of the threshold between “dark” star-less galaxies and galaxies with stellar populations. we discuss a variety of possible formation scenarios for the hi1232+20 system. | (almost) dark hi sources in the alfalfa survey: the intriguing case of hi1232+20 |
this is the third paper of a series where we study the stellar population gradients (sp; ages, metallicities, α-element abundance ratios, and stellar initial mass functions) of early-type galaxies (etgs) at z ≤ 0.08 ≤ 0.08 from the mapping nearby galaxies at apo data release 15 (manga-dr15) survey. in this work, we focus on the s0 population and quantify how the sp varies across the population as well as with galactocentric distance. we do this by measuring lick indices and comparing them to sp synthesis models. this requires spectra with high signal-to-noise ratio which we achieve by stacking in bins of luminosity (lr) and central velocity dispersion (σ0). we find that: (1) there is a bimodality in the s0 population: s0s more massive than 3 × 1010 m⊙ show stronger velocity dispersion and age gradients (age and σr decrease outwards) but little or no metallicity gradient, while the less massive ones present relatively flat age and velocity dispersion profiles, but a significant metallicity gradient (i.e. [m/h] decreases outwards). above 2 × 1011 m⊙, the number of s0s drops sharply. these two mass scales are also where global scaling relations of etgs change slope. (2) s0s have steeper velocity dispersion profiles than fast-rotating elliptical galaxies (e-frs) of the same luminosity and velocity dispersion. the kinematic profiles and sp gradients of e-frs are both more similar to those of slow-rotating ellipticals (e-srs) than to s0s, suggesting that e-frs are not simply s0s viewed face-on. (3) at fixed σ0, more luminous s0s and e-frs are younger, more metal rich and less α-enhanced. evidently for these galaxies, the usual statement that 'massive galaxies are older' is not true if σ0 is held fixed. | galaxy properties as revealed by manga - iii. kinematic profiles and stellar population gradients in s0s |
we present spatially resolved measurements of the stellar initial mass function (imf) in ngc 1399, the largest elliptical galaxy in the fornax cluster. using data from the multi unit spectroscopic explorer (muse) and updated state-of-the-art stellar population synthesis models from conroy et al., we use full spectral fitting to measure the low-mass imf, as well as a number of individual elemental abundances, as a function of radius in this object. we find that the imf in ngc 1399 is heavier than the milky way in its centre and remains radially constant at a super-salpeter slope out to 0.7 re. at radii larger than this, the imf slope decreases to become marginally consistent with a milky way imf just beyond re. the inferred central v-band m/l ratio is in excellent agreement with the previously reported dynamical m/l measurement from houghton et al. the measured radial form of the m/l ratio may be evidence for a two-phase formation in this object, with the central regions forming differently to the outskirts. we also report measurements of a spatially resolved filament of ionized gas extending 4 arcsec (404 pc at dl = 21.1 mpc) from the centre of ngc 1399, with very narrow equivalent width and low-velocity dispersion (65 ± 14 km s-1). the location of the emission, combined with an analysis of the emission line ratios, leads us to conclude that ngc 1399's agn is the source of ionizing radiation. | the stellar population and initial mass function of ngc 1399 with muse |
we present the first single-burst stellar population models, which covers the optical and the infrared wavelength range between 3500 and 50 000 å and which are exclusively based on empirical stellar spectra. to obtain these joint models, we combined the extended miles models in the optical with our new infrared models that are based on the irtf (infrared telescope facility) library. the latter are available only for a limited range in terms of both age and metallicity. our combined single-burst stellar population models were calculated for ages larger than 1 gyr, for metallicities between [ fe / h ] = - 0.40 and 0.26, for initial mass functions of various types and slopes, and on the basis of two different sets of isochrones. they are available to the scientific community on the miles web page. we checked the internal consistency of our models and compared their colour predictions to those of other models that are available in the literature. optical and near infrared colours that are measured from our models are found to reproduce the colours well that were observed for various samples of early-type galaxies. our models will enable a detailed analysis of the stellar populations of observed galaxies. | miles extended: stellar population synthesis models from the optical to the infrared |
in this work, i explore an empirically motivated model for investigating the relationship between galaxy stellar masses, star formation rates and their halo masses and mass accretion histories. the core statistical quantity in this model is the stellar mass assembly distribution, $p(dm_{*}/dt|\mathbf{x},a)$, which specifies the probability density distribution of stellar mass assembly rates given a set of halo properties $\mathbf{x}$ and epoch $a$. predictions from this model are obtained by integrating the stellar mass assembly distribution (smad) over halo merger trees, easily obtained from modern, high-resolution $n$-body simulations. further properties of the galaxies hosted by the halos can be obtained by post-processing the stellar mass assembly histories with stellar population synthesis models. in my particular example implementation of this model, i use the \citet{behroozi13a} constraint on the median stellar mass assembly rates of halos as a function of their mass and redshift to construct an example parameterization of $p(dm_{*}/dt|\mathbf{x},a)$. this smad is then integrated over individual halo mass accretion histories from $n$-body merger trees starting at z = 4, using simple rules to account for merging halos. i find that this a simple model can reproduce qualitatively the bimodal features of the low-redshift galaxy population, including the qualitative split in the two-point clustering as a function of specific star formation rate. these results indicate that models which directly couple halo and galaxy growth through simple efficiency functions can naturally predict the star formation rate bimodality in higher-order statistics of the galaxy field, such as its two-point correlations or galactic conformity signals. | connecting galaxies with halos across cosmic time: stellar mass assembly distribution modeling of galaxy statistics |
we report the detection of morphology-dependent stellar age in massive quenched galaxies (qgs) at z ∼ 1.2. the sense of the dependence is that compact qgs are 0.5-2 gyr older than normal-sized ones. the evidence comes from three different age indicators—{d}n4000, {{{h}}}δ , and fits to spectral synthesis models—applied to their stacked optical spectra. all age indicators consistently show that the stellar populations of compact qgs are older than those of their normal-sized counterparts. we detect weak [o ii] emission in a fraction of qgs, and the strength of the line, when present, is similar between the two samples; however, compact galaxies exhibit a significantly lower frequency of [o ii] emission than normal ones. fractions of both samples are individually detected in 7 ms chandra x-ray images (luminosities ∼1040-1041 erg s-1). the 7 ms stacks of nondetected galaxies show similarly low luminosities in the soft band only, consistent with a hot gas origin for the x-ray emission. while both [o ii] emitters and nonemitters are also x-ray sources among normal galaxies, no compact galaxy with [o ii] emission is an x-ray source, arguing against an active galactic nucleus (agn) powering the line in compact galaxies. we interpret the [o ii] properties as further evidence that compact galaxies are older and further along in the process of quenching star formation and suppressing gas accretion. finally, we argue that the older age of compact qgs is evidence of progenitor bias: compact qgs simply reflect the smaller sizes of galaxies at their earlier quenching epoch, with stellar density most likely having nothing directly to do with cessation of star formation. | morphology dependence of stellar age in quenched galaxies at redshift ∼1.2: massive compact galaxies are older than more extended ones |
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