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this work is devoted to the study of peculiarities in the magnetic coupling of the solar hemispheres over a solar activity cycle. two approaches have been used. we have studied (i) the magnetic coupling of active regions (ars) located in different hemispheres in the vicinity of the central meridian and, simultaneously, in the vicinity of the equator and (ii) the properties and time variation of the meridional component of the equatorial magnetic field derived from a potential-field source surface (pfss) reconstruction at the heliocentric distance of 1.1 solar radii. in the first case, it was shown that most of the ars in the selected pairs were magnetically connected by field lines in their leading parts. in the second case, the magnetic field monthly mean meridional component, bθ, in the equatorial plane, which magnetically connects the two hemispheres, displayed a cyclic time variation. in the process, the extreme values of bθ (both positive and negative) coincided in time with the sunspot maxima, and the amplitude of the bθ extreme values decreased with decreasing height of the sunspot activity cycle. the sign of the bθ extreme value was opposite to the sign of the forthcoming extreme value of the polar field, while the sign of bθ coincided with that of the field lines connecting the leading spots. this means that the polar field is indeed generated by the trailing spots of ars, and the magnetic flux of the leading spots closes through the equator. | magnetic coupling of the solar hemispheres during the solar cycle |
we study periods of elevated energetic particle intensities observed at the l1 sun-earth lagrangian point when the partial energy density associated with energetic (≥80 kev) particles (pep) dominates that of the local magnetic field (pb) and thermal plasma populations (ppls). these periods are not uncommon and are frequently observed prior to the passage of interplanetary (ip) shocks. because of the significant decreases in key solar wind parameters observed during solar cycle 24 [e.g., 1], we were motivated to perform a comparative statistical analysis to determine if the occurrence rate of periods when pep exceeded pb or ppls, or both, differed between solar cycles 23 and 24. we find that the general decrease of pb and ppls in solar cycle 24 was also accompanied by a general decrease of periods with elevated pep. the result is that solar cycle 24 showed a lower number of time intervals dominated by pep. we analyze whether these differences can be related to the properties of the ip shocks observed at l1. incomplete datasets of shock parameters do not show significant differences between solar cycles 23 and 24 that would allow us to explain the difference in the number of periods with pep>pb and pep>ppls. we analyze then the averaged plasma parameters measured in the upstream region of the shocks and find significantly lower solar wind proton temperatures and magnetic field magnitude upstream of ip shocks in solar cycle 24 compared with those in solar cycle 23. these factors, together with the lower level of solar activity, may explain the lower particle intensities in solar cycle 24 and hence the fewer events with pep>pb and pep>ppls. | large energetic particle pressures in solar cycles 23 and 24 |
for the first time, we develop a local time and day of year dependent climatological model in different geomagnetic activity based on 630.0 nm fabry-perot interferometer (fpi) measurements over kelan (38.7°n, 111.6°e) during 2011-2019. with this model, we analyze the regional climatological characteristics of nighttime thermospheric neutral winds, and a comparison is made with two recent versions of the horizontal wind model series (hwms), hwm07 and hwm14. due to the location of kelan far from the northern magnetic pole longitude at middle latitude, the statistical characterizations of meridional and zonal winds show some unique local time, seasonal, solar cycle and geomagnetic activity dependence. there are predominantly annual variations of horizontal winds characterized by rapid transitions from eastward december winds to westward or less eastward june winds and largest equatorward meridional winds during summer months. to some degree, the wind patterns show casual solar activity dependence especially for the zonal component. the maximum southward winds show negative relationship with increasing solar activity in summer months, while the maximum eastward winds present negative trend in winter months. the kp dependencies are characterized by larger westward perturbation winds for all night and enhanced northward winds in the premidnight sector and equatorward surges in the postmidnight sector during strongly active conditions. with increasing solar flux, the westward perturbation winds become weaker at nights. results also reveal that hwm14 predictions are in better agreement with kelan fpi winds in the shape and magnitude than hwm07, and the consistency improves with increasing kp. | climatology of nighttime upper thermospheric winds from fabry-perot interferometer 2011-2019 measurements over kelan (38.7°n, 111.6°e), china: local time, seasonal, solar cycle, and geomagnetic activity dependence |
the latitudinal migration of sunspots toward the equator, which implies there is propagation of the toroidal magnetic flux wave at the base of the solar convection zone, is one of the crucial observational bases for the solar dynamo to generate a magnetic field by shearing of the pre-existing poloidal magnetic field through differential rotation. the extended time series of solar activity indices (esai) elongated the greenwich observation record of sunspots by several decades in the past. in this study, esai’s yearly mean latitude of sunspots in the northern and southern hemispheres during the years 1854 to 1985 is utilized to statistically test whether hemispherical latitudinal migration of sunspots in a solar cycle is linear or nonlinear. it is found that a quadratic function is statistically significantly better at describing hemispherical latitudinal migration of sunspots in a solar cycle than a linear function. in addition, the latitude migration velocity of sunspots in a solar cycle decreases as the cycle progresses, providing a particular constraint for solar dynamo models. indeed, the butterfly wing pattern with a faster latitudinal migration rate should present stronger solar activity with a shorter cycle period, and it is located at higher latitudinal position, giving evidence to support the babcock-leighton dynamo mechanism. | latitudinal migration of sunspots based on the esai database |
sdo/hmi and sdo/aia data for the 24th solar-activity cycle are analyzed using a quicker and more accurate method for resolving π ambiguities in the transverse component of the photospheric magnetic field, yielding new results and confirming some earlier results on the magnetic properties of leading and following magnetically connected spots and single spots. the minimum inclination of the field lines to the positive normal to the solar surface α min within umbrae is smaller in leading than in following spots in 78% of the spot pairs considered; the same trend is found for the mean angle < α> in 83% of the spot pairs. positive correlations between the α min values and the < α> values in leading and following spots are also found. on average, in umbrae, the mean values of < b>, the umbra area s, and the angles α min and < α> decrease with growth in the maximum magnetic field b max in both leading and following spots. the presence of a positive correlation between b max and s is confirmed, and a positive correlation between < b> and s in leading and following spots has been found. themagnetic properties of the umbrae of magnetically connected pairs of spots are compared with the contrast of the he ii 304 emission above the umbrae, c 304. spots satisfying certain conditions display a positive correlation between c 304- land < αl > for the leading (l) spots, and between c 304- l / c 304- fand ll / lf , where ll( lf ) are the lengths of the field lines connecting leading (l) or following (f) spots from the corresponding spot umbrae to the apex of the field line. | comparison of the magnetic properties of leading and following spots and the overlying ultraviolet emission |
the dynamics of coronal holes (chs) during the declining phase of solar cycle 24 is studied based on observational data from the atmospheric imaging assembly (aia), the 19.3 nm channel, of the solar dynamic observatory (sdo). some features of changes in the areas of polar and mid- and low-latitude chs in the period april 1, 2014-december 31, 2019, are revealed by a comparison of the variations in the daily total ch area with the index of the sunspot number. the division of all chs observed in the considered period into polar and nonpolar shows that polar-ch areas dominate and increase while nonpolar-ch areas constantly decrease toward the cycle minimum. polar-ch areas account for ~80% of the total area of all chs considered over the studied period. the total polar-ch area increases toward cycle minimum, which is consistent with the general concept of polar chs as the main source of the sun's dipole magnetic field. however, the second subset, which contains selected isolated chs, shows an interesting behavior in the declining phase of solar activity that was not previously observed. their areas slowly decrease from the maximum to minimum of the solar cycle. this trend is qualitatively consistent with a decrease in sunspot activity toward the minimum, which suggests a physical relationship between the two phenomena. | sunspot activity and coronal holes during the declining phase of cycle 24 |
in this paper the impact of the solar magnetic field on 7be activity concentration in aerosols was investigated. the changes in the 7be activity in aerosols in the period from the second part of 22nd to the second part of 24th solar cycle were mathematically processed using the fourier analysis and the 22 years period was pointed out. it corresponds to the most intense period of the solar polar field strength for the same observed period. the pearson's linear coefficient between the average annual value of 7be activity in aerosols and the solar polar field strength was 0.58. | the impact of the solar magnetic field on 7be activity concentration in aerosols |
energetic charged particle precipitation associated with solar wind perturbations causes enhanced high-frequency radiowave absorption in the high-latitude ionosphere. this study models 38.2 mhz cosmic noise absorption (cna) by utilising measurements from the imaging riometer for ionospheric studies (iris) at kilpisjärvi, finland obtained during solar cycle 23 (1996-2009) associated with the passage of interplanetary coronal mass ejections (icmes) past earth; icmes are a major driver of enhanced geomagnetic activity. superposed epoch analysis suggests that the r6absorption vs. time profile depends on whether icme arrival occurs in the day-time (10-14 mlt) or night-time (22-02 mlt) for iris, with peak absorption occurring ~2-3 h ahead of icme arrival or ~4 h after icme arrival, respectively. we determine which combinations of solar wind and imf parameters show the best correlation with the absorption associated with day-time or night-time arriving icmes using superposed epoch analysis and the least squares estimation method. various combinations of solar wind parameters (including bulk velocity v, density n, and the interplanetary magnetic field north and south components bz and the symh geomagnetic index), have been ranked to obtain the best coupling function for the absorption associated with day- and night-time arriving icmes. the absorption for day-time events is found to correlate closely with the solar wind dynamic pressure, symh, and the northward direction of the bz while the absorption for night-time events is most closely related to the direction of the bz and symh. the coupling functions are found to model the observed absorption successfully, with correlation coefficients of ~0.7-0.8 between the observed and modelled absorption. | empirical modelling of auroral absorption during disturbed periods of interplanetary coronal mass ejection events |
the magnetic field structure of isolated sunspots during the rising phase of activity cycle 24 has been studied using many-hour series of magnetograms of the longitudinal field and images in the continuum taken with the helioseismic and magnetic imager (hmi) on nasa's solar dynamic observatory (sdo). the magnetic axis of the lines of force of the magnetic field of the sunspots was found to be inclined to the west. the average angle of inclination is 1-4° and its magnitude is independent of the heliographic latitude of a sunspot. | magnetic field of sunspots during the rising phase of activity cycle 24 |
in this study, hierarchical self-assembly of photocatalytic nanodisks through non-covalent interactions between spinach-extracted chlorophyll molecules and trimethylammonium hydroxide-coated magnetic iron oxide nanoparticles was discussed. combination of chlorophyll molecules with iron oxide nanoparticles generated an alteration in light absorption at both visible and near-ir region with accompanying enhancement in fluorescence emission. further, photocatalytic role of resulting molecular assembly was studied by means of the photoinduced degradation of methylene blue dye under uv light and direct sun irradiation at neutral ph. in order to enhance the long-term stability of the hybrid nanocatalyst, commercially available cellulose membrane was used as a support and magnetic recovery and reusability was achieved where the nanocatalyst retained more than 90 % of its efficiency even after four cycles. this simple strategy could initiate the development of new materials for wastewater treatment including membrane-based technologies. on the other hand, their sunlight-induced photocatalytic activity could easily be conducted to dye-synthesized solar cells or their enhanced photoluminescence can provide a strong basis for future bioimaging tools. | photoactive nanocomplex formed from chlorophyll assembly on tma-coated iron oxide nanoparticles |
the study of variations in total solar irradiance (tsi) and spectral irradiance is important for understanding how the sun affects the earth's climate. a data-driven approach is used in this article to analyze and model the temporal variation of the tsi and mg ii index back to 1947. in both cases, observed data in the time interval of the satellite era, 1978 - 2013, were used for neural network (nn) model-design and testing. for this particular purpose, the evolution of the solar magnetic field is assumed to be the main driver for the day-to-day irradiance variability. first, we design a model for the mg ii index data from f10.7 cm solar radio-flux using the nn approach in the time span of 1978 through 2013. results of mg ii index model were tested using various numbers of hidden nodes. the predicted values of the hidden layer with five nodes correspond well to the composite mg ii values. the model reproduces 94% of the variability in the composite mg ii index, including the secular decline between the 1996 and 2008 solar cycle minima. finally, the extrapolation of the mg ii index was performed using the developed model from f10.7 cm back to 1947. similarly, the nn model was designed for tsi variability study over the time span of the satellite era using data from the physikalisch-meteorologisches observatorium davos (pmod) as a target, and solar activity indices as model inputs. this model was able to reproduce the daily irradiance variations with a correlation coefficient of 0.937 from sunspot and facular measurements in the time span of 1978 - 2013. finally, the temporal variation of the tsi was analyzed using the designed nn model back to 1947 from the photometric sunspot index (psi) and the extrapolated mg ii index. the extrapolated tsi result indicates that the amplitudes of solar cycles 19 and 21 are closely comparable to each other, and solar cycle 20 appears to be of lower irradiance during its maximum. | temporal variations in solar irradiance since 1947 |
the preliminary results of solar filaments distinguished in daily h-alpha observations at kodaikanal (1912-2002) are presented. to mark the boundaries of solar filaments, methods based on automated procedures of marking low-contrast objects on the solar disk, as well as editing of the marked boundaries in a semiautomated manner, were developed. the characteristics of solar filaments were analyzed. latitudinal diagrams of filaments number in 15-23 activity cycles were constructed. as is shown, one maximum in the filament latitudinal distribution may be clearly distinguished during activity cycles in both hemispheres. this maximum is located slightly higher (θ 25°-30°) than the sunspot distribution maximum (θ 14°-17°). however, there are no other local maxima related to the zonal structure of the large-scale magnetic field (makarov and sivaraman, 1989). | reconstruction of a hundred years series of solar filaments from daily observational data |
this work studies the influence of the structure of inner heliospheric magnetic field on the propagation of jovian electrons from jupiter to the earth orbit. beginning from 1974, 13-month variations of relativistic jovian electron fluxes were recorded by spacecraft near the earth. 22 synodic cycles are analysed. the best connection in each cycle was found within a narrow longitudinal interval with an angular divergence of the planets 230 ± 20°, when the parker field line connecting the two planets is formed at solar wind speed 450 ± 50 km s-1. such invariability for more than 45 yr could not be accidental. we attribute the observed phenomenon to the long-term presence of recurrent stationary structures in the solar wind generated near the sun. this assumption is confirmed by comparing the time profiles of the solar wind speed measured over all solar rotations in the solar activity minima in 1975 and 2007-2008. | jovian electrons at the earth orbit and stationary structures in the solar wind |
in this thesis, various studies leading to better understanding of the 11-year solar cycle and its theoretical modeling with the flux transport dynamo model are performed. although this is primarily a theoretical thesis, there is a part dealing with the analysis of observational data. the various proxies of solar activity (e.g., sunspot number, sunspot area and 10.7 cm radio flux) from various observatory including the sunspot area records of kodaikanal observatory have been analyzed to study the irregular aspects of solar cycles and an analysis has been carried out on the correlation between the decay rate and the next cycle amplitude. the theoretical analysis starts with explaining how the magnetic buoyancy has been treated in the flux transport dynamo models, and advantages and disadvantages of different treatments. it is found that some of the irregular properties of the solar cycle in the decaying phase can only be well explained using a particular treatment of the magnetic buoyancy. next, the behavior of the dynamo with the different spatial structures of the meridional flow based on recent helioseismology results has been studied. a theoretical model is constructed considering the back reaction due to the lorentz force on the meridional flows which explains the observed variation of the meridional flow with the solar cycle. finally, some results with 3d ftd models are presented. this 3d model is developed to handle the babcock-leighton mechanism and magnetic buoyancy more realistically than previous 2d models and can capture some important effects connected with the subduction of the magnetic field in polar regions, which are missed in 2d surface flux transport models. this 3d model is further used to study the evolution of the magnetic fields due to a turbulent non-axisymmetric velocity field and to compare the results with the results obtained by using a simple turbulent diffusivity coefficient. | understanding the behavior of the sun's large scale magnetic field and its relation with the meridional flow |
electrons accelerated in the jupiter magnetosphere are usually registered by near-earth spacecraft under optimal magnetic connection between the earth and jupiter, taking place once in 13 months (earth- jupiter synodic period). during the period of minimal solar activity between 23 and 24 cycles in 2007-2009 electrons of mev energies were observed practically at each of 14 solar rotations (more than a year), which requires extremely long quasistationary state of inner heliosphere with constant earth- jupiter connection. to explain this situation the model with long living magnetic trap, co-rotating with the sun, was suggested. passing by the jupiter this trap captures electrons, which then are registered by subsequent passing of the trap by the earth. | jovian electrons as an instrument of investigation of the interplanetary medium structure |
the objective of this study is to investigate the solar-cycle variation of the areas of solar open magnetic flux regions at different latitudes. the data used in this study are the radial-field synoptic maps from wilcox solar observatory from may 1970 to december 2014, which covers 3.5 solar cycles. our results reveal a pole-to-pole trans-equatorial migration pattern for both inward and outward open magnetic fluxes. the pattern consists of the open flux regions migrating across the equator, the regions generated at low latitude and migrating poleward, and the regions locally generated at polar regions. the results also indicate the destruction of open flux regions during the migration from pole to equator, and at low latitude regions. the results have been published in scientific reports (huang et al.<xref rid="r4" ref-type="bibr">2017</xref>) | solar open magnetic flux migration pattern over solar cycles |
the solar activity has hemispheric asymmetries. the levels of activity are different on the two hemispheres on intermediate and longer time scales. during four schwabe cycles the progress of the northern hemispheric activity precedes the southern one, while in the next four cycles the southern cycle takes over the preceding role (muraközy and ludmány, mon. not. roy. astron. soc.419, 3624, 2012; muraközy, astrophys. j.826, 145, 2016). the interplanetary magnetic field is formed by the distribution of the solar magnetic fields and the outward-streaming solar wind. the present study intends to show how the solar-hemispheric predominance affects the interplanetary and geophysical magnetic field. the interplanetary and geophysical data sets have been chosen from various sources such as the components of the interplanetary magnetic field [b ], cosmic-ray data, ap, aa, and dst geomagnetic indices, while the solar-hemispheric asymmetry has been examined by using sunspot data from greenwich photoheliographic results (gpr) and debrecen photoheliographic data (dpd). | connection between solar hemispheric toroidal cycles and geomagnetic variations |
the present paper reports coordinated ionospheric irregularity measurements at optical as well as gps wavelengths. optical measurements were obtained from tiny ionospheric photometer (tip) sensors installed onboard the constellation observing system for meteorology, ionosphere, and climate (cosmic) satellites. gps radio signals were obtained from a dual frequency gps receiver operational at calcutta (22.58°n, 88.38°e geographic; geomagnetic dip: 32.96°; 13.00°n, 161.63°e geomagnetic) under the scintillation network decision aid (scinda) program. calcutta is located near the northern crest of equatorial ionization anomaly (eia) in the indian longitude sector. the observations were conducted during the unusually low and prolonged solar minima period of 2008-2010. during this period, four cases of post-sunset gps scintillation were observed from calcutta. among those cases, simultaneous fluctuations in gps carrier-to-noise ratios (c/no) and measured radiances from tip over a common ionospheric volume were observed only on february 2, 2008 and september 25, 2008. fluctuations observed in measured radiances (maximum 0.95 rayleigh) from tip due to ionospheric irregularities were found to correspond well with c/n0 fluctuations on the gps links observed from calcutta, such effects being noted even during late evening hours of 21:00-22:00 lt from locations around 40° magnetic dip. these measurements indicate the existence of electron density irregularities of scale sizes varying over several decades from 135.6 nm to 300-400 m well beyond the northern crest of the eia in the indian longitude sector during late evening hours even in the unusually low solar activity conditions. | multi-wavelength coordinated observations of ionospheric irregularity structures from an anomaly crest location during unusual solar minimum of the 24th cycle |
results of experiments on polarized radio sounding of the outer solar corona using the helios spacecraft from 1975 to 1984 are presented. the characteristic parameters of the temporal spectra of fluctuations in the faraday rotation of the plane of polarization for heliocentric distances from 3.5 to 5.5 solar radii are obtained. the absolute level of these fluctuations and, consequently, the level of fluctuations of the magnetic field, is almost independent of the solar activity. it is well known that the global structure of the solar wind varies with the solar cycle such that there is slow solar wind at low latitudes and fast solar wind at high latitudes during solar minima. in contrast, a slow solar wind dominates at all latitudes during solar maxima. one explanation for the invariance of the fluctuations observed by sounding the circumsolar plasma is that the mean magnetohydrodynamic turbulence of the low-latitude, slow solar wind depends weakly on the phase of the solar cycle. | solar wind magnetic field turbulence over the solar activity cycle inferred from coronal sounding experiments with helios linear-polarized signals |
magnetohydrodynamics (mhd) describes the complex interaction between magnetic fields and plasmas that are responsible for much dynamic behavior in the sun and many other cosmic objects. this chapter introduces the fundamental equations and their physical effects, including the basic physics inherent in the equations of induction and motion and the key process of magnetic reconnection for converting magnetic energy into other forms. mhd is important in astrophysical processes such as magnetoconvection, magnetic flux emergence, flux ropes, spots, atmospheric heating, wind acceleration, flares, and eruptions. in particular, the focus is on the generation of magnetic fields by dynamo action. | chapter 7 - magnetohydrodynamics and solar dynamo action |
in this article we construct the 3d magnetic field of solar active region noaa12673 using two nonlinear force-free field (nlfff) methods. the event chosen for the study was the x9.3 class flare on september 6, 2017, which was the largest flare of solar cycle 24. we analyzed the evolution of the free-force field parameter \alpha around the flare occurrence. we used the vector magnetogram from helioseismic and magnetic imager (hmi) instruments on board of the solar dynamics observatory (sdo) in the full disk format and spaceweather hmi active region patch (sharp) format, for two hours before and after the x9.3 class flare. the comparison of the two codes, that use different algorithms and two different sets of data, shows that there are similarities and differences. our investigation revealed that, in spite we found the same behaviour of the alpha parameter evolution during the major flare development, after that different results were obtained. | a comparison of two methods for solar nonlinear force-free field extrapolation |
reconstruction of regions with an open configuration of magnetic force lines was carried out according to synoptic hα maps over a period of more than 100 years. it is shown that the maximum area of open structures in the cycle of solar activity is reached in the descending phase, 1÷2 years before the onset of the minimum. the total area of open structures in the current cycle n has a high correlation (r ~ 0.8) with the amplitude of the next activity cycle n + 1. there is also a secular envelope with a maximum in the middle of the 20th century. | evolution of structures with an open magnetic flux over a hundred years |
here, we compare the sunspot counts and the number of sunspot groups (sgs) with variations of total solar irradiance (tsi), magnetic activity, ca ii k-flux, faculae and plage areas. we applied a time series method for extracting the data over the descending phases of solar activity cycles (sacs) 21, 22 and 23, and the ascending phases 22 and 23. our results suggest that there is a strong correlation between solar activity indices and the changes in small (a, b, c and h-modified zurich classification) and large (d, e and f) sgs. this somewhat unexpected finding suggests that plage regions substantially decreased in spite of the higher number of large sgs in sac 23 while the ca ii k-flux did not decrease by a large amount nor was it comparable with sac 22 and relates with c and def type sgs. in addition to this, the increase of facular areas which are influenced by large sgs, caused a small percentage decrease in tsi while the decrement of plage areas triggered a higher decrease in the magnetic field flux. our results thus reveal the potential of such a detailed comparison of the sg analysis with solar activity indices for better understanding and predicting future trends in the sacs. | temporal variations of different solar activity indices through the solar cycles 21-23 |
in this paper we have focused on drift of irregularities using amplitude scintillations for period january 2011 to december 2015. the data of vhf amplitude scintillations and all sky imager at kolhapur has been used to obtain the drift of ionospheric irregularities. the drift is compared with velocities of thermospheric wind obtained by hwm-07 (horizontal wind model-07) and of epbs (equatorial plasma bubbles). the results are in good agreement with model data. also, the pattern of drift in scintillation data matches well with velocity of epbs, mainly during equinoctial months. to examine the possible effect of magnetospheric disturbance on the dynamics of the irregularities we have compared the drift on magnetically disturbed nights with the monthly averaged quiet nights drift. zonal velocity pattern on magnetically disturbed nights shows reversal in the direction of eastward zonal drift around midnight. the deviation of plasma drift on disturbed nights from monthly averaged quiet night drift shows maximum effect of magnetic activity around midnight. the monthly averaged peaks of the zonal drift increases with increasing 10.7 cm solar flux. | dynamics of ionospheric irregularities in increasing phase of 24th solar cycle at kolhapur [16.4°n, 74.2°e] |
we have analyzed the debrecen photoheliographic data (dpd) and the solar optical observing network (soon) sunspot group data during the period 1977 - 2015 and find that during the maximum of solar cycle 23 there is a large difference in the mean meridional motion of sunspot groups determined from dpd and soon data. | long-term variations in meridional motion of sunspot groups: comparison of dpd and soon data |
it is known that the poloidal field is at its maximum during solar minima, and that the behaviour during this time acts as a strong predictor of the strength of the following solar cycle. this relationship relies on the action of differential rotation (the omega effect) on the poloidal field, which generates the toroidal flux observed in sunspots and active regions. we measure the helicity flux into both the northern and southern hemispheres using a model that takes account of the omega effect, which we find offers a strong quantification of the above relationship. we find that said helicity flux offers a strong prediction of solar activity up to 5 years in advance of the next solar cycle. | magnetic helicity as a predictor of the solar cycle |
we report the results of an analysis of the variation of the proper rotation of several destabilized satellites over many-year long time intervals. the cause of the cyclic variations of the proper rotation period of "midas-7" satellite, which has been orbiting the earth since 1963 at an altitude of 3700 km, have long been unclear. these variations could not be explained either by the influence of the terrestrial atmosphere and terrestrial magnetic field, or by solar activity. based on the results of 40-year long observations of "midas-4," "midas-6,", and "midas-7" satellites it was established that their proper rotation exhibits not only dissipative braking variations, but also long-period variations with the periods of 477 days ("midas-4"), 466 days ("midas-6"), and 346 days ("midas-7") with different amplitudes. these variations in the case of the above satellites have well-defined resonance nature. an explanation of the processes found is proposed based on the results of this study and simulations of the observed orbital dynamics of the satellites. long-period variations of the proper spacecraft rotation arise as a result of the combined effect of the gravitational fields of the earth, moon, and sun depending on the orientation of their orbital planes in space. the amplitudes of such variations is determined by the inclination of satellite orbits to the equator: the closer it is to the pole (i.e., to 90°), the stronger the effect. | influence of the gravitational fields of the moon and the sun on long-period variations in the proper rotation of "midas" satellites |
the polar magnetic field near the cycle minimum is known to correlate with the height of the next sunspot maximum. there is reason to believe that the hemispheric coupling can play an important role in forming the next cycle. the meridional component of the large-scale magnetic field can be one of the hemispheric coupling indices. for our analysis we have used the reconstructed data on the large-scale magnetic field over 1915-1986. we show that in several cycles not only the height but also the general course of the cycle can be described in this way about 6 years in advance. this coupling has been confirmed by the currently available data from 1976 to 2016, but the ratio of the meridional field to the total absolute value of the field vector has turned out to be a more promising parameter. in this paper it was calculated at a height of ∼70 mm above the photosphere. the date of the forthcoming minimum is estimated using this parameter to be mid-2018; using the global field as a forecast parameter gives a later date of the minimum, early 2020. | meridional component of the large-scale magnetic field at minimum and characteristics of the subsequent solar activity cycle |
we compare the specral-polarized obsevations of magnetic fields in two powerful solar flares of october 28, 2003 (of x17.2 / 4b class) and july 17, 2004 (of x1.1 / 2n class) using fei and d1 nai lines. we found that in both flares the effective magnetic field beff was stronger in the chromosphere than in the photosphere. the strongest magnetic field (4600 gs) was measured at the chromospheric level of a weaker flare, and this field was 1.6 times stronger than the magnetic field in the nearest sunspot. comparing the obtained results with similar data by lozitska et al [8] for flares of 1981 and 1989 (i.e., for cycles nos. 21 and 22), we can see a significant difference. in both flares of 2003 and 2004, which relate to 23rd cycle of solar activity, we have beff (fei) < beff(d1) for splitting of emission peaks, whereas for flares of cycles nos. 21 and 22, the inverse in equality beff (fei)>beff(d1) istrue. this result is still unclear and requires additional scrutiny on a base of new observational data. | comparison of chromospheric and photospheric magnetic fields in two solar flares of x1.1/4n and x17.2/4b importance |
this paper is related to analysis of the weddell sea anomaly (wsa) and the mid-latitude summer nighttime anomaly (msna) observed by the low altitude satellite demeter during nighttime between 2004 and 2010. this time interval corresponds to the decrease of the solar cycle 23 which was unusually long. it appears that, if these two anomalies have a peak in local summer (december in the southern hemisphere for the wsa, june in the northern hemisphere for the msna), the anomalies are also observed during the months around december and june with a decreased intensity. but at the end of the solar cycle 23 the summer peaks dramatically decrease and even relatively more quickly than the solar index f10.7. this phenomenon is much more significant for the wsa. it is shown that the mechanism producing the two anomalies (thermospheric neutral winds and magnetic declination effects) is strengthened by the solar ionization which is active during the night above the wsa and the msna areas. but at solar minimum, this mechanism is weakened. these results are valid at the satellite altitude (660 km) and may vary at lower altitudes. | variations of the main nighttime ionospheric density anomalies observed by demeter during the descending phase of solar cycle 23 |
the total solar irradiance (tsi) is considered one of the main factors determining the terrestrial climate, and its variations are included in many numerical models evaluating the effects of natural as compared to anthropogenic factors of climate change. for the purposes of climate change, it is important to estimate both past and future tsi variations, which are caused by variations of the solar magnetic fields. various proxies are used for reconstructing the long term evolution of tsi, which have some inevitable limitations leading to big uncertainties. we suggest an independent proxy-geomagnetic activity records, and present a reconstruction of tsi which supports higher long term tsi variability than generally accepted, and a prediction for a decrease in tsi in the following cycles, which can be taken into account in models of the expected future climate variability. | reconstruction of the long term variations of the total solar irradiance from geomagnetic data |
the total solar irradiance (tsi) index of solar activity attracts the attention of a wide scientific audience due to its direct influence on the earth's climate. a number of reconstructions of inter-decadal tsi variability have been extended back to the early holocene but these estimates still remain uncertain and depend on the model and proxy data used for the particular reconstruction. here we compare the accuracy of nonlinear forecasts for different reconstructions, confirmed by the global hurst exponent and pointwise hölder regularity estimates with the only persistent, regular and predictable reconstruction. the deterministic reconstruction identified predicts a further slow decrease in average tsi level in cycle 25. we applied the empirical mode decomposition to determine major tsi modes which mainly describe long-term changes in the sun's radiative output. we found a crucial role of 100- and 200-yr cycles in the occurrence of long-term tsi depressions related to grand minima in the sun's magnetic activity. a necessary condition for grand minima occurrence is established in terms of the major tsi modes. based on the relationship, we conclude that a moderate tsi depression is possible in future decades without a grand minimum. | long-term changes in total solar irradiance and their predictions |
the energy of the sun transformed on the earth's surface into heat is the main component in the formation of the earth's climate. therefore, climate processes significantly depend on changes in the solar activity index (ca). this can be the basis for projections of crop yields. we considered the time series of data on the yield of grain crops as the imposition of a long-term trend, several cyclical components and a random component. the data between points on the time scale for the index of solar activity sn is consistent with the monthly, and for yield, with annual intervals. the dynamics of changes in yield curves of grain crops has a wave character. the grain yield curves smoothed over a 47-year study period highlighted a general trend. spectral analysis revealed short waves of changes in grain yield with periods of 2-3 years and with amplitudes for different crops from 0.3-0.5 to 2-2.5 tons/hectare. the values of the harvest depend most of all on the values of the ca indices in the months of sowing grain, going out into the pipe and ripening. the results of the calculations show that high values of the correlation coefficients are achieved by comparing the course of the yield of selected grain crops not with the 11-year, but with the 22-year magnetic cycle of hale's solar activity. after subtracting it, spectral analysis with a confidence of 90% indicated the existence of quasi-periodic components with a period value of about 2.134±0.062 years. the search for possible periodic processes in the solar system, which could cause a change in yields with a marked period value, showed that the gravitational interaction of the planets has the same periodicity at opposition of earth and mars. analysis of the data presented in the work shows that the maximum yields were in those years when at distances less than 0.55 au. the planets were in opposition in spring and summer during the main growing season of the analyzed crops. | correlation of yield of grain crops with changes in the index of solar activity |
a comparative analysis of evolution of latitude distributions of solar magnetic fields of various scales is presented. using the local photospheric magnetic fields (lmf) represented by the magnetic fields of sunspots for cycles 12-23 it is found that the width of the sunspot generating zone is closely related to the magnitude of the total magnetic flux of sunspots. it is demonstrated that latitude-time distributions of the lmf and absolute strengths of the background magnetic field (bmf) in the latitude range ± 40 ° are very similar and the time variations of power indices of the bmf and lmf are highly correlated. it is found that power characteristics of the bmf and lmf in cycles 21-23 are in close relation to the size of the low-latitude zone of solar activity. it is shown that the speed of the polar drift of the bmf of a given polarity tends to increase in epochs of solar cycle maximums. the obtained regularities can be used as diagnostic criteria for determination of adequate physical models of solar cyclicity. | some properties of latitude-time evolution of local and background solar magnetic fields |
the kinematic modeling of the solar convection zone remains the workhorse of the solar dynamo to understand the solar cycle. during the past several years, the major progress in understanding the solar cycle using kinematic models is as follows. (1). the babcock-leighton (bl) mechanism was confirmed to be at the essence of the solar cycle. (2). the scatter of sunspot tilt angles is identified as a major cause of solar cycle irregularities. (3). the important roles of the magnetic pumping in the dynamo process are recognized. (4). some 3d kinematic bl type dynamo models have been developed. as a key part of the solar dynamo loop, the surface observable part of the bl mechanism makes the physics-based solar cycle prediction feasible. including the effects of the tilt scatter on the polar field generation, the possible strength of the subsequent cycle can be predicted when a cycle starts for a few years. | state-of-the-art of kinematic modeling the solar cycle |
sunspots are active regions on the surface of the sun having strong magnetic fields. activity level of the sun shows long-time scale phenomena known as grand episodes-grand maxima and grand minima. present study examines grand episodes shown by sunspot numbers (1090-2017), using methods of wavelet transform and sinusoidal regression. time interval analysed includes two grand maxima and four grand minima. interval in between grand episodes are regular oscillations. phase changes found from periodicity analysis clearly show the presence of upcoming grand episodes. the forthcoming grand episodes are suggested to be two grand minima which are likely to occur between the years 2100-2160 and 2220-2300. | prediction of upcoming grand episodes of solar activity |
here we report our recent prediction of the solar cycle 25 based on a newly developed scheme, which is used to investigate the predictability of the solar cycle over one cycle. the scheme is a combination of the empirical properties of solar cycles and a surface flux transport model to get the possible axial dipole moment evolution at a few years before cycle minimum, by which to get the subsequent cycle strength based on the correlation between the axial dipole moment at cycle minimum and the subsequent cycle strength. we apply this scheme to predict the large-scale field evolution since 2018 onwards. the results show that the northern polar field will keep on increasing, while the southern polar field almost keeps flat by the end of cycle 24. this leads to the cycle 25 strength of 125 +/- 32, which is about 10% stronger than cycle 24 according to the mean value. | a prediction of the solar cycle 25 |
we have analyzed the data on yearly mean international sunspot number (rz) during the period 1610 - 2015 and orbital positions (ecliptic longitudes) of the giant planets in each 10-day interval during the period 1600 - 2099. we determined mean absolute difference (>$\overline{\psi _d}$>) of the orbital positions of the giant planets in each interval. we find that there exits a good correlation between cycle amplitude (rm, i.e. the maximum value of rz) and the value of >$\overline{\psi _d}$> at cycle maximum, suggesting that on longer time scales low/high solar activity associated with less/large spread in orbital positions of the giant planets (i.e. with a low/high value of >$\overline{\psi _d}$>). | long-term variations in solar activity and planetary configurations |
we analyzed the features of the longitudinal distribution of the areas of solar spots during the solar activity minima, from the 11th cycle to the last minimum, based on data provided by the greenwich observatory and the marshall research center. we discovered that the solar spots evolved in one or two neighboring bands (in terms of longitude), the carrington longitude of which smoothly displaced from the east to the west, in the phase of the deep minimum in all of the considered cases. the spots at the high latitudes associated with a "new" cycle evolved on the same longitude bands. all of this led to the noticeable longitudinal asymmetry of magnetic fluxes related to the spots and flocculi. based on our research, we propose the hypothesis that a nonaxisymmetric component of the total magnetic flux of the sun is generated, together with the dipole component, by the solar dynamo mechanism, which is a typical feature of the phase of a minimum between the solar activity cycles. | the features of longitudinal distribution of solar spots during the last 13 solar activity minima |
the solar photosphere is seething with a vast amount of magnetic flux tangled on scales much smaller than the resolution scale of solar telescopes that can be investigated by considering the hanle effect. in 2007, near a minimum of the solar cycle, we started a synoptic program to explore possible variations of such hidden magnetic flux with the solar cycle, through the application of a differential hanle effect technique on observations of scattering polarization in c2 molecular lines in the region around 514.0 nm. the observing program is still ongoing generally with the cadence of about one month. the observations obtained up to now, which include the recent maximum of the solar activity, don't show large variations of the turbulent unresolved magnetic field. if the apparent constancy is confirmed through the current cycle, than it will have important implications, since it provides hints on the existence of a local dynamo effect at granular and sub-granular scale, uncorrelated with the global magnetic field varying with the solar cycle. | synoptic program to measure the evolution of the photospheric magnetic field during a solar cycle |
the almost stately evolution of the global heliospheric magnetic field pattern during most of the solar cycle belies the intense dynamic interplay of photospheric and coronal flux concentrations on scales both large and small. the statistical characteristics of emerging bipoles and active regions lead to development of systematic magnetic patterns. diffusion and flows impel features to interact constructively and destructively, and on longer time scales they may help drive the creation of new flux. peculiar properties of the components in each solar cycle determine the specific details and provide additional clues about their sources. the interactions of complex developing features with the existing global magnetic environment drive impulsive events on all scales. predominantly new-polarity surges originating in active regions at low latitudes can reach the poles in a year or two. coronal holes and polar caps composed of short-lived, small-scale magnetic elements can persist for months and years. advanced models coupled with comprehensive measurements of the visible solar surface, as well as the interior, corona, and heliosphere promise to revolutionize our understanding of the hierarchy we call the solar magnetic field. | the evolution of the solar magnetic field |
the paper reviews recent studies of cyclicity of magnetic activity of the sun based on the αω-dynamo model. it is noted that there is a functional dependence between the observed values of the poloidal bp and toroidal bt magnetic fields. this allows predicting the amplitude and the strength of cycle for the measured field bp at the beginning of the cycle. nevertheless, for a long time no positive correlations between the characteristics of sunspots cycle (wolf number or the total area of spots) and polar magnetic flux at the end of the cycle were found. as it turned out later, this was due to the fact that the α-effect of babcock-leighton, defined by tilt angles of the bipolar magnetic fields, turbulent diffusion and meridional circulation, leading to regeneration of the poloidal field, is characterized by random fluctuations in time and space. the situation changed drastically after the parameter of magnetic strength of cycle was introduced, which is a product of the area of spots cycle and tilt angles of the bipolar magnetic groups. within the framework of the αω-dynamo this indicates that the surface α effect of babcock-leighton leads to the generation of the poloidal magnetic field at the end of the current cycle, and its assimilated parameter is an integral component of future forecasts based on the solar dynamo models. relying on the data which cover the time span of more than a century, recent studies have established that the memory interval of cycle is limited only by one cycle. | the role of the alpha effect of babcock-leighton in the generation of poloidal magnetic field of the sun |
we studied the aa geomagnetic index ( aa index daily average) behavior on a monthly timescale using data from 1868 to 2015 for cycles 11-24. we identified solar- and lunar-associated periodicities in the aa time series and found statistically significant aa minima values a few days before the full moon and high aa values during the new moon. when considering all the cycles, it was clear that the deepest aa minima occurred during the aa descending activity phase. however, when the cycles were separated according to the direction of the interplanetary magnetic field (imf), the aa minima came from the contribution of cycles with the imf pointing toward the sun (type 1). furthermore, during the descending phase of cycles with the imf pointing away from the sun (type 2), the smallest aa index values were found along with smaller changes compared to type 1 cases. this behavior implies that during type 1 cycles there are larger aa perturbations than during type 2 cycles. it is very likely that the mechanisms responsible for the aa monthly behavior are a combination of solar and lunar effects that depend on several factors: (a) the moon phases (new and full moon), (b) the phase of the solar cycle (ascending or descending), and (c) the direction of the interplanetary magnetic field (away or toward the sun). | new perspectives on contributing factors to the monthly behavior of the aa geomagnetic index |
specific features of the magnetic configuration, morphological structure, dynamics, and evolution of sunspot groups of the current (24th) cycle of solar activity with high flare activity are considered. the gradients of longitudinal magnetic fields at places of δ-configuration are calculated. the main finding is a time delay of 24-30 h between the time when the magnetic field gradient reaches a critical level of 0.1 g/km and the time when the first of powerful flares occurs in the active region. the study is based on data from the sdo and goes-15 spacecrafts and ground-based solar telescopes (tst-2 at the crimean astrophysical observatory of the russian academy of sciences and the 150-foot telescope at the mount wilson observatory). | sunspot groups with high flare activity: specific features of magnetic configuration, morphology, and dynamics |
we compare changes in the solar global magnetic field (gmf) given by the distribution of magnetic fields on the source surface and spot activity characterized by wolf numbers, the number of spots, and their area reflecting the dynamics of local magnetic fields of active regions during cycles 21 to 24 (1976-2015). the results indicate that the changes in the gmf and spot activity have certain differences, both in different cycles generally and in the phases of growth, maximum, and decline in each individual cycle. the maximum and minimum correlations between the gmf and spot activity are observed in cycles 22 and 24, respectively. the maximum correlation is reached in growth phases (cycles 21, 22, and 24) and in the phase of decline (cycle 23), which can be associated with the fact that the phase of decline in cycle 23 is anomalously extended. almost no correlation between the gmf and spot activity can be found at the phases of the maximum and early beginning of decline in all cycles. this can be associated with structural reorganization and sign change in the gmf. | comparison of changes in the global magnetic field and spot activity in cycles 21 to 24 |
the long-term data of the ionospheric alfven resonance (iar) observations recorded at the ukrainian antarctic station "akademik vernadsky" from 2002 to 2013 and at sayan solar observatory (mondy, russia) from 2010 to 2013 are analyzed. iar fine spectral structure is studied and a previously unknown effect of splitting of the several lowest resonance modes is discovered. the diurnal and seasonal dependencies of this effect are investigated as well as the dependences of the probability of iar and splitting detection on solar and geomagnetic activities in the 11-year cycle. the morphological features of the splitting frequency behavior are analyzed and three main characteristic periods of the splitting are identified, namely: the development, the stationary period and the disappearing. possible mechanisms of the splitting effect are suggested. | observations and analysis of the ionospheric alfven resonance mode structure in a complete 11-year solar cycle |
we report results of analysis of the north-south asymmetry of solar activity, solar magnetic fields. the analysis is based on the sunspot data, 1875-2015 (http://solarscience.msfc.nasa.gov/greenwch.shtml), large-scale solar magnetic field (solar mean magnetic field, smmf) and solar polar magnetic field time series, 1975-2015 (http://wso.stanford.edu). to study long-term changes of solar activity asymmetry we applied analysis of cumulative sum. cumulative sum averages short-periodic changes and identifies long-term periodicity. minimum of cumulative sum of sunspot area mean monthly values time series occurs in ∼1910, maximum - in ∼1980. perhaps this is branch growth of long-term (∼140-years) cycle of solar activity asymmetry. cumulative sums of polar magnetic field of different pole have ∼22-years periodicity. change of cumulative sum of smmf time series has different character. but long-run trend with intervals of positive and (or) negative polarity of ∼22 years is observed. | longterm changes of solar activity asymmetry |
asymmetry, a well established fact, can be extracted from various solar atmospheric activity indices. although asymmetry is being localized within short time scale, it also persists at different time scales. in the present study we examine the character and nature of asymmetry at various time scales by optimizing the data set, in units of carrington rotations (crs), for sunspot area (sa) and soft x-ray flare index (fi sxr). we find from three solar cycles (21-23) that at a small time scale (viz., daily, crs and monthly) activity appears to be asymmetric with less significance. at larger time scales (≥01 crs) strength of asymmetry enhances. number of significant asymmetry points probably depends upon the solar heights. for different combination of data, asymmetry strength appears to be lowered at certain periods ∼06, ∼12, ∼18 crs (164, 327 and 492 days i.e., harmonics of ∼1.3 years. owing to similar behavior of emergence of magnetic flux, it is conjectured that emergence of flux on the surface probably contributes to the asymmetry of the solar activity. | lowering of asymmetry |
plasma sheet particles transported earthward during times of active magnetospheric convection can interact with exospheric/thermospheric neutrals through charge exchange. the resulting energetic neutral atoms (enas) are free to leave the influence of the magnetosphere and can be remotely detected. enas associated with low-altitude (300-800 km) ion precipitation in the high-latitude atmosphere/ionosphere are termed low-altitude emissions (laes). remotely observed laes are highly nonisotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90°. the geomagnetic emission cone of laes can be mapped spatially, showing where proton energy is deposited during times of varying geomagnetic activity. in this study we present a statistical look at the correlation between lae flux (intensity and location) and geomagnetic activity. the lae data are from the mena imager on the image satellite over the declining phase of solar cycle 23 (2000-2005). the sym-h, ae, and kp indices are used to describe geomagnetic activity. the goal of the study is to evaluate properties of laes in ena images and determine if those images can be used to infer properties of ion precipitation. results indicate a general positive correlation to lae flux for all three indices, with the sym-h showing the greatest sensitivity. the magnetic local time distribution of laes is centered about midnight and spreads with increasing activity. the invariant latitude for all indices has a slightly negative correlation. the combined results indicate lae behavior similar to that of ion precipitation. | statistical correlation of low-altitude ena emissions with geomagnetic activity from image/mena observations |
the geoeffect of extremely low solar (sunspot) activity starting from the last solar minimum is one of the major space science issues. the present study examines long-term changes of geomagnetic responses seen as dst, kp, and al indices to the same solar wind conditions (density, velocity, magnetic field, and their products) using the nasa omni hourly values up to august 2014. both decadal averages (1965 to 1974, 1975 to 1984, 1985 to 1994, 1995 to 2004 that approximately correspond to solar cycles #20 to 23, respectively, and from 2005) and annual averages indicate that the geomagnetic activity for a given solar wind condition, namely the sun-earth coupling efficiency, decreased quantitatively from around 2006 until now compared to the previous four decades. the decrease remains even after the euv flux (using f10.7 index) is considered and is more obvious in the low-latitude geomagnetic disturbances (dst) than in the high-latitude geomagnetic disturbances (al). the results cannot be explained by existing explanations including the ionospheric conductivity effect in the magnetosphere-ionosphere coupling system. | decreased sun-earth energy-coupling efficiency starting from 2006 |
solar time series manifests nonlinear and non-stationary behaviors, and perhaps multi-modal dynamical processes operating in solar magnetic indicators. in the present work, the novel ensemble empirical mode decomposition (eemd) is applied to study the monthly distribution of sunspot areas produced by the extended time series of solar activity indices (esai) database in the time interval from 1821 january to 1989 december. it is established that the quasi-periodic variations of monthly sunspot areas consist of at least three well-defined dynamical components: one is the short-term variations which are obviously smaller than one year, the second one is the mid-term variations with periodic scales varying from 1 year to 15 years, and the last component is the periodic variation with periodicities larger than 15 years. the analysis results indicate the eemd technique is an advanced tool for analyzing the weakly nonlinear and non-stationary dynamical behaviors of solar magnetic activity cycle. | ensemble empirical mode decomposition applied to long-term solar time series analysis |
the long-standing disparity between the sunspot number record and the hoyt and schatten (1998, h&s) group sunspot number series was initially resolved by the clette et al. (2014) revision of the sunspot number and the group number series. the revisions resulted in a flurry of dissenting group number series while the revised sunspot number series was generally accepted. thus, the disparity persisted and confusion reigned, with the choice of solar activity dataset continuing to be a free parameter. a number of workshops and follow-up collaborative efforts by the community have not yet brought clarity. we review here several lines of evidence that validate the original revisions put forward by clette et al. (2014) and suggest that the perceived conundrum no longer need to delay acceptance and general use of the revised series. we argue that the solar observations constitute several distinct populations with different properties which explain the various discontinuities in the series. this is supported by several proxies: diurnal variation of the geomagnetic field, geomagnetic signature of the strength of the heliomagnetic field, and variation of radionuclides. the waldmeier effect shows that the sunspot number scale has not changed over the last 270 years and a mistaken scale factor between observers wolf and wolfer explains the disparity beginning in 1882 between the sunspot number and the h&s reconstruction of the group number. observations with replica of 18th century telescopes (with similar optical flaws) validate the early sunspot number scale; while a reconstruction of the group number with monthly resolution (with many more degrees of freedom) validate the size of solar cycle 11 given by the revised series that the dissenting series fail to meet. based on the evidence at hand, we urge the working groups tasked with producing community-vetted and agreed upon solar activity series to complete their work expeditiously. | several populations of sunspot group numbers - resolving a conundrum |
multiple multi-skip time-distance measurement schemes were developed to image the sun's far-side active regions(ars), by measuring the travel-time shifts of acoustic waves that travels globally and gets reflected at the far-side solar surface. the measurement procedure were applied on 11 year of sdo/hmi doppler observations, and over 8000 far-side images of the sun have been obtained with a 12-hr temporal cadence. the mean travel-time-shifts in these images, each of which is made from 14 images using 14 different measurement schemes, serve as the main indicator of the existence of far-side ars and unsurprisingly vary with the phases of the solar cycle. however, these temporal variations do not show good correlations with the magnetic activity in their respective northern or southern hemisphere, but show perfect correlation with the global-scale magnetic activity. what causes the temporal variations in the travel-time shifts measured in these long-travel-distance acoustic waves? we investigate four possible reasons: travel-time deficits in far-side ars, contamination of oscillation signals by near-side magnetic fields, solar radius change, and cumulative effects of waves' reflections in magnetic regions. | long-term evolution of acoustic travel times measured in sdo/hmi time-distance far-side images |
solar activity predictions using the data assimilation approach have demonstrated great potential to build reliable long-term forecasts of solar activity. in particular, it has been shown that the ensemble kalman filter (enkf) method applied to a non-linear dynamo model is capable of predicting solar activity up to one sunspot cycle ahead in time, as well as estimating the properties of the next cycle a few years before it begins. these developments assume an empirical relationship between the mean toroidal magnetic field flux and the sunspot number. estimated from the sunspot number series, variations of the toroidal field have been used to assimilate the data into the parker-kleeorin-ruzmakin (pkr) dynamo model by applying the enkf method. the dynamo model describes the evolution of the toroidal and poloidal components of the magnetic field and the magnetic helicity. full-disk magnetograms provide more accurate and complete input data by constraining both the toroidal and poloidal global field components, but these data are available only for the last four solar cycles. in this presentation, using the available magnetogram data, we discuss development of the methodology and forecast quality criteria (including forecast uncertainties and sources of errors). we demonstrate the influence of limited time series observations on the accuracy of solar activity predictions. we present enkf predictions of the upcoming solar cycle 25 based on both the sunspot number series and observed magnetic fields and discuss the uncertainties and potential of the data assimilation approach. the research is funded by the nsf shine program ags-1622341. | long-term prediction of solar activity using magnetogram data and ensemble kalman filter |
the dynamic activity of the sun, governed by its cycle of sunspots modulate our solar system space environment creating space weather. severe space weather leads to disruptions in satellite operations, telecommunications, electric power grids and air-traffic on polar routes. we use four different machine-learning algorithms, all of them belonging to a class called recurrent neural networks, for forecasting. we apply one of these algorithms -- reservoir computing -- to forecast the magnetic field generated by a stochastic dynamo model. we find that the forecast is inaccurate for times longer than the first cycle. we next apply the algorithms to forecast solar sunspot data. by comparing forecasts for cycles 22, 23, and 24 we conclude that a minor variation of reservoir computing algorithm performs the best. the standard reservoir computing forecasts that solar cycle 25 is going to last about ten years, the maxima is going to appear in the year 2024 and the maximum number of sunspots is going to be 113 (±15). a minor variation of the standard algorithm gives the forecast for duration and peak timing as that of the standard algorithm, but the forecast for the peak amplitude is 124 (±2) -- within the upper bound of the standard algorithm. we conclude that sunspot cycle 25 is likely to be a weak, lower than average solar cycle, somewhat similar in strength to sunspot cycle 24. | a machine-learning forecast for sunspot cycle 25 |
understanding the solar cycle is a fundamental and important objective in solar physics. recent studies have revealed correlations between variations of the poleward transport of photospheric magnetic fields with properties of both magnetic field in solar active regions as well as their decay products. features such as poleward surges often play an outsized role in advecting flux away from the activity belts into polar regions, and therefore affect solar cycle activity. this report describes our plans and reviews preliminary results investigating the effects of active region-modified zonal and meridional flows on flux evolution and the solar cycle. | understanding solar cycle magnetic evolution with properties of solar active regions |
the solar polar fields play a crucial role in sustaining the solar dynamo mechanism. observations and computational modelling indicates that the surface dynamics of active regions mediated via plasma flows, which leads to the polar field build-up, is a fundamental aspect of the solar dynamo mechanism; in fact, this surface mediated flux dynamics also known as the babcock-leighton mechanism, is now implicated to be the leading contributor to the sun's polar field, and thus also provides a window to the future solar cycle. this emergent understanding is one of the major drivers of novel mission concepts aiming to image the solar high latitudes from out of the ecliptic locations. based on numerical simulations of the near-surface magnetic field dynamics and the sun's polar landscape, here we discuss what new insights may be provided by out-of-the ecliptic solar physics missions. | dynamics of the sun's polar field: possible insights from out of the ecliptic observations |
total solar irradiance (tsi) reconstructions using sunspot area and facular brightening as predictors capture most tsi variability observed by satellites, and are used to estimate solar forcing since 1610 through sunspot count records. interdecadal and longer timescale variability in tsi is difficult to constrain, however, due to two major sources of uncertainty. first, the stability of the satellite-derived tsi record is hampered by long-term drift due to instrumentation degradation, calibrations between up to 9 satellite records with varying instrumental configurations, and limited periods of overlap between observing missions. second, tsi reconstructions using sunspot counts are susceptible to uncertainties in the sunspot record, as well as nonlinearity or nonstationarity in the sunspot-tsi relationship. we present a linear mixed effects model framework to evaluate the degree to which sunspots are an accurate and stationary predictor of tsi. we explore the sunspot-tsi relationship between solar cycles using magnetic activity proxies, including solar radio flux and the mg ii index. this analysis provides an estimate of the inter-cycle variability of tsi during solar minima, which is relevant for exploring whether a grand minima of solar activity, such as the maunder minimum, maintains an accurate and stable sunspot-tsi relationship. an improved record of long-term solar forcing will help distinguish between internal variability and external forcing as sources of climate variability. | evaluating the degree to which sunspots are an accurate and stationary predictor of total solar irradiance |
it is considered that changes of the north atlantic's heat content can be a source of surprises in the evolution of the present-day climate, especially the climate of europe. to investigate this problem, the rapid monitoring program has been organized. however, results of such monitoring still cover too short a time interval to reach any particular conclusions. in this study, using wavelets, heat content variations in the 0-700 and 0-2000 m oceanic layers were analyzed since the mid-20th century. their relationships with mean temperature variations of the 0-100 m layer, as well as with earlier analyzed temperature variations of the north atlantic sea-surface temperature, also are analyzed. it is found that, against a total increase in heat content, variations of all specified characteristics reveal a periodicity similar to the known approximately 22-year-long hale heliomagnetic activity cycle. in the 0-700 m layer, this periodicity leading on its phase not only the corresponding periodicity in the 0-2000 m layer, which corresponds well to the generally accepted opinion that heat content anomalies extend from top ocean layers down, but also in the mean temperature of the 0-100 m layer, as well as in the sea-surface temperature. this makes it possible to consider that heliomagnetic activity immediately influences the upper 0-700 m layer of the ocean, thence extending down and up. | conductors of heat content changes of the north atlantic ocean layers |
the solar acoustic emission is closely related to solar convection and magnetic field. understanding the relation between the acoustic emission and the phase of a solar cycle is important to understand the dynamics of solar cycles and excitation of acoustic waves. in this work we use 4 years of sdo/hmi data from 05/2010 to 04/2014, covering the growing phase of the solar cycle 24, to study the acoustic emissions of the whole sun and of only the quiet sun regions respectively, at multiple frequency bands. we also analyze the correlations between the acoustic emissions and solar activity level indexed by daily sunspot number and magnetic flux. the results show that the correlation between the whole-sun acoustic emission and solar activity level is negative for low frequencies at 2.5-4.5 mhz, with a peak value around -0.9, and is positive for high frequencies at 4.5-6.0 mhz, with a peak value around 0.9. for high frequencies, the acoustic emission excess in sunspot halos overwhelms the emission deficiency in sunspot umbrae and penumbrae. the correlation between the quiet-sun acoustic emission and solar activity level is negative for 2.5-4.0 mhz and positive for 4.0-5.5 mhz, with peak values over ±0.8. this shows that the solar background acoustic power, with active regions excluded, is indeed varying during a solar cycle, implying the excitation frequencies or depths are highly related to the solar magnetic field. | correlation between solar acoustic emission and phase of the solar cycle |
geomagnetic indices are widely used to identify events of interest and specify space weather conditions. ae [1] and dst [2] are two such indices. recently supermag [3] have produced analogous indices, sme and smr, at higher spatial and temporal resolution. we perform a statistical comparison across the last four solar maxima to determine the effect of improved spatial resolution. we find that differences between ae and sme in a given solar cycle maximum are of the order of difference found between one solar maximum and the next. using ae or sme give different results for solar cycle activity dependence. the electrojet indices, ae and sme, are the instantaneous difference between the largest positive h-component disturbance and the largest negative disturbance registered by any two stations in the network. typically, ae uses 12 stations and sme uses 110 stations. when we compare the distributions of the indices, sme systematically exceeds ae. we build a simplified model of a gaussian-distributed sheet current, over a square plane of fixed magnetometers. we vary the number of magnetometers in the model plane. we confirm that increased spatial resolution qualitatively accounts for the higher values registered by sme. the ring current indices, dst and smr, are averages of the h-component disturbances measured at all stations in the network. dst uses 4 stations and smr typically uses 100 stations. to construct dst and smr, magnetometer observations are mapped to the magnetic equator by a linear operation which implies that dst and smr are related by a linear shift. the distribution of dst should then collapse onto smr under linear rescaling. we confirm that this is the case. these results provide insight into how the considerable body of work obtained using ae and dst relates to sme and smr. [1] davis, t. n., sugiura, m. (1966) jgr, 71(3):785-801. [2] sugiura, m. (1964) ann. int. geophys., 35(9) [3] gjerloev, j. w. (2012) j. geophys. res., 117, a09213, doi:10.1029/2012ja017683 | ae, dst and their supermag counterparts: the effect of improved spatial resolution in geomagnetic indices |
the solar cycle, a cyclic change with a period of about 11 years, is the waxing and waning of the solar magnetic field with time. other indicators of solar activity follow a similar trend, as inferred from direct measurements above the solar surface. however, measuring the magnetic field beneath the surface cannot be accomplished through direct methods. past helioseismic studies have revealed a strong correlation between the variations in solar acoustic oscillation frequencies of the waves propagating below the sun's surface and magnetic activity indicators above the surface, allowing the frequencies to serve as an activity proxy for the interior. during the activity minimum between cycles 23 and 24, several studies identified different minimum periods in the layers below and above the surface raising questions on the origin of the solar cycles. in this paper, we evaluate the current minimum and present results on the identified epochs of minimum. this allows us to investigate the connection between various layers of solar interior and the atmosphere. the oscillation frequencies that we use for this study are derived from the global oscillation network group (gong) observations while several indicators of the solar activity are used for above surface conditions. this work is carried out through the national solar observatory research experiences for undergraduates (reu) program, which is funded by the national science foundation (nsf) through award no. 1659878. | investigating solar acoustic oscillations and surface activity during the current minimum |
we analyze the total intensity (i) and circularly-polarized (v) ratan-600 radio scans obtained at the 3.3-17.0 ghz range during the 23-24 minimum of solar activity. it is found that, in the 3.37-6.8 ghz range, the circular polarization varies linearly with the ew position. the slope is measured at different frequencies and different times. the value of the slope for a given frequency varies with time indicating a dependence with p and b solar angles. it is not clear what could be the reason of such behavior. a possible interpretation of this dependence could be made in terms of the variation of the magnetic field component along the line of sight, which plays an important role in the polarized flux observed in the case of bremsstrahlung emission. | the solar radio emission during the minimum between the 23-24 cycles of solar activity |
the solar magnetic field waxes and wanes with time, going through a cyclic change with a period of about 11 years, commonly known as the solar cycle. other indicators of solar activity follow a similar trend, as inferred from direct measurements above the solar surface. however, there are no direct methods to measure magnetic fields or other forms of solar activity below the surface. past studies have demonstrated strong correlations between the variations in oscillation frequencies of the waves propagating below the sun's surface and above-surface magnetic activity indicators, therefore the frequencies serve as an activity proxy for the interior. we use oscillation frequencies derived from the global oscillation network group's (gong) observations to study the conditions in the convection zone while various indicators of the solar activity are used for above surface conditions. we have identified the previous minimum, between cycles 23 and 24, was deeper than the current minimum, while the current minimum is wider. in addition, similar to the previous minimum, different layers in the convection zone during the current minimum sensed minima at different times. this work is carried out through the national solar observatory research experiences for undergraduates (reu) program, which is funded by the national science foundation (nsf) through award no. 1659878. | investigating solar minimum below and above the solar surface: is the current solar minimum different from the previous minimum? |
active regions, which are mainly responsible for the energetic blast from the sun so-called flare, have a highly concentrated magnetic field. almost all flares have been attributed to the dynamics of its magnetic field on the photosphere. one method to know the changings is through studying their properties using magnetogram data. the data that are obtained from helioseismic magnetic imager (hmi) instruments onboard solar dynamics observatory (sdo) have a good temporal resolution which can make a better analysis. we analyze three properties of photospheric magnetic field namely total photospheric magnetic free energy (totpot), total unsigned vertical current (totusjz) and total unsigned current helicity (totusjh) of the active region (ar) 12740 which produced almost m-class flare at the very minimum phase of solar cycle 24. then, we compared their values to the average values of all the corresponding parameters for almost one solar cycle. the results showed that the values of each parameter in ar 12740 was below the average values of c-flare-productive ars. the totpot was half of the average while totusjh and totusjz were around one-third of the average. | photospheric magnetic field properties of active region 12740 |
we present composite white-light images of the 2 july 2019 total solar eclipse, from the minimum of the solar-activity cycle. with separate high-resolution ground-based images, one of them made of 646 individual images with such a wide field that it exceeds the fields of view of the naval research laboratory's c2 and c3 coronagraphs aboard esa's solar and heliospheric observatory, we have composites based on observations from the cerro tololo inter-american observatory and the centerline of totality at la higuera in chile. we compare the resolution of the coronal streamers and other magnetic phenomena of the corona. we also show continuity from features on the solar surface as observed from nasa's solar dynamics observatory and noaa's goes-16 solar ultraviolet imager (suvi). acknowledgments: jmp's eclipse research receives major support from grant ags-903500 from the solar terrestrial program, atmospheric and geospace sciences division, u.s. national science foundation. we had additional student support from the massachusetts nasa space grant consortium; sigma xi; the global initiatives fund at williams college; and the university of pennsylvania. | compositing eclipse images from the ground and from space |
recent exploration of mars sets the stage for relevant fundamental questions and research themes. what initial conditions and pre-noachian events were inherited by the noachian? 1) planetary origin: location and growth rates; volatile budget; earliest bombardment history? 2) crustal formation & evolution: nature of magma ocean, its aftermath; primary/secondary crust formation; associated outgassing history? 3) geodynamic evolution & petrogenetic history: core formation, ensuing mantle convection patterns; magnetic field; redox state(s), petrogenetic evolution; timing, role of basins. 4) primary & secondary atmospheres: nature of each, transition, inheritance? what was the nature and evolution of the noachian climate? 1) nature of ancient atmosphere & climate: what were noachian "ambient conditions": `warm and wet' or `cold and icy'? how did volatile species/quantities change with time; volcanic outgassing, relationship to evolving atmospheric pressure; nature/scale/duration of ambient climate perturbations; losses and influence on mean annual temperature? 2) candidate climate perturbations: identify perturbations to the ambient atmosphere? role of seasonal, spin axis/orbital variations, impacts, greenhouse gas input, hydrolysis, clouds, solar variability? 3) water cycle: initial water inventory, changes with time; vertically integrated hydrological cycle; oceans? how was water partitioned (sources, sinks, d/h, loss to space)? 4) sulfur cycle: total s budget, partitioning with time; nature of volcanic s exsolution with evolvingatmospheric pressure; s cycle (sources, sinks, evolution); origin of valles marineris interior layered deposits? 5) mineralogy/geomorphology evolution & implications: causes of phyllosilicate/sulfate diversity of occurrences? origin of salts/carbonates/silica-rich deposits? relation to ln-h climate and weathering processes, rates. how are crater degradation and valley network/closed-basin/open-basin lake origin linked to ln-h mineralogy, climate? 6) formation/evolution of life: evolving paradigms include an ambient `cold and icy' climate with warming perturbations: what strategies/proxies are needed to explore potential biotic environments on extremely cold surfaces above a warmer, wetter, geochemically active `mars underground'? | the noachian climate of mars: overview of critical mars system science questions |
radiation environment in the earth magnetosphere can not be considered without taking into account the physical conditions in interplanetary space due to solar activity. therefore, any realistic model of radiation inside the magnetosphere should take into account the physical condition determined by the models out of it. since the flux of galactic and solar cosmic rays in the magnetosphere based on the model of radiation outside the magnetosphere with an indispensable view of the magnetic field of the earth, due to changes in the solar wind, interplanetary shock waves and magnetic field. these factors are also influence the models of trapped radiation and circular current. particularly, this report addressed to the methodological issues of generalization of experimental data to the level of computational models, which is unchanged properties of predicting all kinds of extreme situations. the complex of these problems has long been discussed under the pressure of public attention in connection with the problems of weather forecasting and hydrology. in the field of space weather the problem of operational models evaluation (so called "metric & validation" activity) is also of great interest now. in the light of changes in the factors of solar activity in the last minimum and in the solar cycle 24, the report discusses the problems of modeling particle fluxes outside the magnetosphere. current status of near- earth radiation modeling including radiation belt particles transport, acceleration and losses will be discussed as well from the experimental and theoretical viewpoint. | space weather models for radiation conditions outside and inside of the earth's magnetosphere |
magnetosheath jets are transient localized structures of enhanced dynamic pressure observed downstream of the earth's bow shock. they may exhibit an increase of velocity reaching solar wind levels, while their density is typically much higher than typical magnetosheath and solar wind values. jets have been associated to several magnetospheric effects such as, magnetopause reconnection, excitations of surface eigenmodes and even direct plasma penetration in the magnetosphere. while their exact origin is unknown, many mechanisms have been proposed. one of the most prominent explanations involves the interaction of solar wind with local inclinations of the bow shock (ripples) while others include solar wind discontinuities, and foreshock structures.in this work, by using magnetosphere multiscale (mms) we show in-situ observations of a super-magnetosonic magnetosheath jet being generated as a direct result of the bow shock reformation cycle. the observed jet origin appears to be the result of the dynamical evolution of the shock and the emergence of a spatially de-attached compressive magnetic structure that acts as a local shock front. due to this, the solar wind particles are effectively transferred downstream without experiencing a strong interaction with the shock, which allows compressed high velocity plasma to be observed downstream of the bow shock.the proposed mechanism does not require external phenomena (e.g., solar wind discontinuities) or specific configuration of the bow shock (e.g., ripples) to take place. on the contrary, it allows the magnetosheath jet phenomenon to directly originate from the dynamical evolution of the quasi-parallel collisionless shock. | high-speed magnetosheath jet generation due to shock reformation |
a statistical study of the subauroral polarization stream (saps) over the north american sector is conducted by using the millstone hill incoherent scatter radar measurements from 1979 to 2019. the key features of saps and its associated plasma parameters, such as ion vertical flow, electron density, ion temperature, and electron temperature, are analyzed via a superposed epoch analysis method. the characteristics of these parameters are investigated with respect to magnetic local time, season, geomagnetic activity, solar activity, and interplanetary magnetic field (imf) orientation, respectively. the main results are as follows: (1) there is obvious ion upward flow around saps peak region. both of them exhibit similar variation patterns with a larger magnitude around dusk than midnight, in winter than summer, during active geomagnetic periods than quiet time, in solar minimum than maximum, and under imf conditions with negative by and negative bz. (2) saps is usually associated with a midlatitude trough of 15--20% depletion. the trough has specific local time and seasonal preference, which is more pronounced in postmidnight and around equinoxes. (3) the subauroral ion and electron temperature exhibit 3--8% enhancement associated with saps. both of them have more considerable enhancement during geomagnetically active periods, and during midnight than dusk. condition for ion temperature enhancement is more favored during low solar activity periods, while the electron temperature enhancement is almost constant within the solar cycle. | analysis of saps using the millstone hill incoherent scatter radar data |
the latitude-belt in which active regions appear migrates equatorward as solar cycle progresses. however, often these active regions tend to appear at the same longitude where an active region previously occurred. on one hand, they don't appear at one specific longitude always, on the other hand they also don't appear randomly all over the solar surface. there exists a systematic persistence as well as some randomness in spatio-temporal evolutionary patterns of active regions. by implementing the `kmean' clustering algorithm of machine learning, we evaluate the centroids of each cluster of points representing a given polarity of bipolar active regions in synoptic magnetograms, and apply information theory to the latitude and longitude coordinates of these active regions to derive the information flow at specific latitude-longitude locations with time. we discuss the persistence of locations and information flow from the past to the future. we will determine the spatial and temporal scale of the information flow and persistence of the active regions. | estimating persistent and random components in spatio-temporal evolutionary patterns of active regions using information theoretic approach |
we have studied deep minima of 11-year solar activity cycles 13–14, 14–15, 22–23, 23–24, 24–25, using the rgo and usaf/noaa sunspot group catalogs. all of them have a large number of spotless days. nonetheless, active longitudes as preferred zones, where sunspots occur, appear at this solar cycle phase. analysis of synoptic maps and wso daily magnetograms reflecting the structure of a weak large-scale field shows a non-axisymmetric component of the solar magnetic field. at solar minimum in the structure of the large-scale magnetic field, there are regions of the magnetic field of positive and negative polarity elongated along the meridian and crossing the equator. the most pronounced of them are located in the zone of active longitudes and are often connected with the polar magnetic fields. we discuss the possible nature of the meridional structures of the large-scale field during solar minimum. this might be due to giant convection cells with a banana cell structure. | active longitudes and the structure of the large-scale magnetic field at solar minimum |
based on synoptic magnetic maps, we use spherical harmonic functions to decompose the global magnetic field of the sun. through the expansion coefficients, the power spectrum cl, and its zonal component clz and sectorial component cls for order l are defined. through two sampled synoptic maps, it is easy to show that the multipole moments in solar active years are much stronger than those in the quiet years. we decomposed the synoptic maps for carrington rotations (crs) 1625 to 2224, i.e., corresponding solar cycles 21 - 24, and studied the evolution of multipole moments. except for the monopole, the power spectra cl for most moments have an obvious 11-year period. the dipole and octupole in solar cycle 22 are much stronger than in the other three cycles. the zonal components of dipole and octupole are opposite to the phases of most modes, while the sectorial components of them are consistent with most phases. in addition, compared to the phase of the yearly sunspot number, the phases of most multipoles are relatively delayed, except for the zonal modes of the quadrupole and 32-pole (l =5 ). we find that the zonal mode of l =5 is very strong, which leads ahead of the phase of the yearly sunspot number for about 10 crs. additionally, unlike the other modes, it has a strong 5.5-year period. then, the zonal mode of l =5 is mainly induced by the magnetic field of the sunspots, which is further confirmed in this work. | the evolution of multipole moments for the global solar magnetic field |
we consider several tracers of magnetic activity that separate cycle-dependent contributions to the background solar magnetic field from those that are independent of the cycle. the main message is that background fields include two relative separate populations. the background fields with a strength up to 100 mx cm-2 are very poorly correlated with the sunspot numbers and vary little with the phase of the cycle. in contrast, stronger magnetic fields demonstrate pronounced cyclic behaviour. small-scale solar magnetic fields demonstrate features of fractal intermittent behaviour, which requires quantification. we investigate how the observational estimate of the solar magnetic flux density b depends on resolution d in order to obtain the scaling in bd = -k in d + a in a reasonably wide range. the quantity k demonstrates cyclic variations typical of a solar activity cycle. k depends on the magnetic flux density, i.e. the ratio of the magnetic flux to the area over which the flux is calculated, at a given instant. the quantity a demonstrates some cyclic variation, but it is much weaker than in the case of k. the scaling is typical of fractal structures. the results obtained trace small-scale action in the solar convective zone and its coexistence with the conventional large-scale solar dynamo based on differential rotation and mirror-asymmetric convection. here we discuss the message for solar dynamo studies hidden in the above results. | cycle-dependent and cycle-independent surface tracers of solar magnetic activity |
stream interaction regions (sirs) tend to increase geomagnetic activity when they interact with the earth's magnetosphere. the study of the sirs-magnetosphere interaction becomes important for its effects on space weather. based on in-situ observations from the wind spacecraft, we analyze the characteristics of a set of sirs registered during the years 2007-2008 and 2018-2019 corresponding to the descending phase of the solar cycles 23 and 24, respectively. in this research, we mainly focus on examining the physical characteristics of the solar wind (sw), the radial width of the sirs, the relative position of the stream interface (si), the latitudinal orientation of the si, the momentum transfer between the fast and slow sw, as well as the dynamic, thermal and magnetic pressure in the unperturbed fast and slow sw, the presence of associated shocks and their correlation with geomagnetic activity. the geoeffectiveness generated as a result of the sirs-magnetosphere interaction was measured using the global indices: kp and sym-h. finally, we examine the properties of the source region of fast sw that generated each sir by using euv images. | stream interaction regions registered in the descending phase of the solar cycles 23 and 24 |
we study long-lived activity complexes using stackplots of magnetic activity derived from nso/solis synoptic magnetograms. we focus on the kinetic helicity below the surface determined with ring-diagram analysis applied to full-disk dopplergrams from sdo/hmi during solar cycle 24. the kinetic helicity of activity complexes follows the hemispheric helicity rule with mainly positive values in the southern hemisphere and negative ones in the northern hemisphere. to distinguish between active and quiet regions, we divide the data into subsets with high and low levels of activity and create stackplots of surface magnetic activity and subsurface kinetic helicity for each subset. the distribution of flares in a stackplot resembles closely that of the high-activity subset. the flare-productive locations in long-lived complexes produce, on average, the same number of flares as those of short-lived ones. however, long-lived complexes have a larger number of these locations and thus a higher flare-production rate than short-lived ones. we will present the latest results. | long-lived activity complexes, their kinetic helicity, lifetime, and flare activity |
we report an analysis of low-frequency waves in the ulysses magnetic field data that arise from newborn interstellar pickup he+. ulysses observations of waves excited by interstellar h+ have already been reported, but in this analysis we identify waves due to the ionization of he atoms. while neutral he can reach inside 1 au in significant numbers whereas interstellar neutral h cannot, we find that most of the waves due to he+ are seen at moderate to low heliolatitude beyond 3 au. this may reflect the nature of the orbit where ulysses spends a greater fraction of its time in this region, or it may reflect the turbulence conditions. our analysis will address this and related questions. | observations of low-frequency waves excited by newborn interstellar pickup he+ as seen by the ulysses spacecraft |
proxies of solar activity have revealed repeated grand minima that occur with a certain regularity associated with the well-known gleissberg and süss/devries cycles. these and other prominent cycles in the spectrum of solar activity are also seen in the spectrum of the planetary torque exerted on the solar tachocline, which has revived the hypothesis of a planetary influence on solar activity. it is not clear, however, how the extremely weak planetary forcing could influence the solar magnetic activity. here, we suggest that stochastic resonance could explain the necessary amplification of the forcing and provide numerical evidence from stochastic time-delayed dynamo models. if the intrinsic noise of the solar dynamo allows for a frequent switching between active and quiescent stable states, tiny periodic forcings can be greatly amplified, provided the dynamo is poised close to a critical point. such a forcing could be caused by a tidal modulation of the minimal magnetic field required for flux-tube buoyancy. | stochastic resonance could explain recurrence of grand minima |
we present an analysis of 9 periodic oscillations observed in the neutral mesospheric density, temperature and wind during the declining phase of solar cycle 23 from 2004 to 2009. mesospheric densities, temperatures and winds near 90 km are derived using data from the davis station (68.5°s, 77.9°e; magnetic latitude, 74.6°s), svalbard (78.3°n, 16°e, magnetic latitude, 75°n) and tromsø (69.6°n, 19.2°e, magnetic latitude, 67.1°n) meteor radars. spectral analysis indicates that the pronounced periodicity of 9 days observed in the mesosphere densities temperatures and winds are associated with variations in solar wind high-speed streams and recurrent geomagnetic activity. a morlet wavelet analysis shows that the time evolution of the 9-day oscillation in the neutral mesosphere densities is similar to those variations in the solar wind and in planetary magnetic activity index, kp in the declining phase of solar cycle 23. these results demonstrate a direct coupling between sun's corona (upper atmosphere) and the earth's mesosphere. | response of mesosphere to energetic particle precipitation |
to understand the influence of the sun on earth's system, long and accurate measurements of solar irradiance are a prerequisite. the available direct measurements of solar irradiance since 1978 are clearly not sufficient for this purpose. this stimulated development of models used to reconstruct past solar irradiance variations from alternative observations. the main driver of the irradiance variations on time scales of days to millennia is the evolution of the solar surface magnetic field in form of dark sunspots and bright faculae and network. therefore, models require input data describing the contributions of these various magnetic regions on the sun at earlier times. unfortunately, records that can be used to describe the facular and network contributions are barely longer than the direct irradiance measurements. thus, irradiance reconstructions to earlier periods have to rely on sunspot data alone. data that have hardly been used for solar irradiance reconstructions until now are full-disc solar observations in the ca ii k line. such data exist since 1892 from various observatories and include all the needed information describing faculae and the network. however, they are plagued by a bunch of various problems and artefacts, and recovering the non-linear response of the photographic material to the radiation is non-trivial since the required information is usually missing, too. we have developed a method to process ca ii k observations from various sources and demonstrated the higher accuracy achieved by our method compared to other techniques presented in the literature. here we use the carefully reduced ca ii k observations from multiple archives to reconstruct solar irradiance variations. | reconstructing solar irradiance from ca ii k observations |
a hyperbolic cell-centered finite volume solver (hccfvs) is first proposed to obtain the potential magnetic field solutions prescribed by the solar observed magnetograms. by introducing solution gradients as additional unknowns and adding a pseudo-time derivative, hccfvs transforms second-order poisson equation into an equivalent first-order as well as pseudo-time-dependent hyperbolic system. thus, instead of directly solving the second-order poisson equation, hccfvs obtains the solution to the poisson equation by achieving the steady-state solution to this first-order hyperbolic system. the code is established in fortran 90 with message passing interface parallelization. to preliminarily demonstrate the effectiveness and accuracy of the code, two test cases with exact solutions are first performed. the numerical results show its second-order convergence. then, we apply the code to the solar potential magnetic field problem that is often approximated analytically as an expansion of spherical harmonics. a comparison between the potential magnetic field solutions demonstrates the capability of our new hccfvs to adequately handle the solar potential magnetic field problem, and thus it can be used as an alternative to the spherical harmonics approach. furthermore, hccfvs, like the spherical harmonics approach, can be used to provide the initial magnetic field for solar corona or solar wind magnetohydrodynamic (mhd) models. using the potential magnetic field obtained by hccfvs as input, the large-scale solar coronal structures during carrington rotation (cr) 2098 have been studied. meanwhile, hccfvs automatically deals with the poisson projection method to keep the magnetic field divergence-free constraint during the time-relaxation process of achieving the steady state. the numerical results show that the simulated corona captures main solar coronal features and the average relative magnetic field divergence error is maintained to be an acceptable level, which again displays the performance of hccfvs. | hyperbolic cell-centered finite volume method for obtaining potential magnetic field solutions |
the dominant form of mass and energy transport between the sun and the planetary magnetospheres of uranus and neptune remains an open question. the interaction between the solar wind and a planetary magnetosphere is often parameterized in terms of the upstream alfvénic mach number, m a , with lower values enabling enhanced rates of energy and mass exchange between the interplanetary and planetary environments. here we perform a comprehensive analysis of upstream m ain the solar system using data spanning from 0.3 au to 75 au, collected by the helios 1 & 2, voyager 1 & 2, and pioneer 10 & 11 spacecraft from 1972-2005. we find that systematic increases in solar wind magnetic pressure during periods of high solar activity lead to lower-than-expected m a upstream of the giant planets, similar to those measured at mercury, where magnetic reconnection plays a dominant role in plasma transport. these values combined with the significant tilt of the magnetic dipole axes at uranus and neptune and weak internal plasma sources likely result in amplified solar-wind-magnetospheric coupling at solar maximum. | the solar cycle dependence of the solar wind interaction with the ice giants |
it is shown that the solar corona rotates differentially at all heliocentric distances up to the source surface. as the distance increases, the differential rotation gradient decreases, and the rotation becomes more and more rigid. at small distances, the corona at latitudes above ≈ ± 40° rotates faster than the photosphere at the same latitudes. the type of the rotation depends also on the phase of the activity cycle. the differential rotation gradient is the largest in the vicinity of the cycle minimum. it is shown that time variations in the coronal rotation characteristics are associated with the tilt of the magnetic equator of the sun. based on the concept that the differential rotation of the corona reflects the rotation of deep subphotospheric layers, we compared the changes in the coronal rotation characteristics with distance with the helioseismic data and showed their satisfactory agreement. the results obtained allow us to suggest that the rotation of the solar corona can be used as indicator of the differential rotation of subphotospheric layers and calculate the nature of some current sheets in heliosphere/ | differential rotation of the solar corona and its importance for helioseismology |
with the introduction from june 2015 of a new methodology for estimation of wolf numbers w (or wsn — wolf sunspot number), this series was corrected from january 1749 to may 2015, i.e. a new version of the series wsn was proposed. the greatest transformation affected the cycles of a statistically reliable part of the series (since, 1849), which was clearly reflected in their amplitude correction and, accordingly, in the long-period component of the series, determining the epoch of maximum/minimum solar activity. the quasi-biennial oscillations available in the solar magnetic field and in the total flux of its radiation also manifest themselves in a number of parameters of the earth ionosphere and evaluation of their transformation degree is of high significance. this paper compares the characteristics of the frequency interval of the quasi-biennial oscillations of both versions of a series. | transformation of the characteristics of quasi-biennial oscillation in a new version of the series of wolf (relative sunspot) numbers |
in this work we will show the behavior of the horizontal component h of the earth magnetic field (emf) along the seasons during the period of solar cycle 24 lasting from 2009 to 2019. by means of continuous measurements of geomagnetic components (x, y) of the emf, we compute the horizontal component h at the earth"s surface. the data are recorded with a time resolution of one minute at tamanrasset observatory in algeria at the geographical coordinates of 22.79° north and 5.53° east. these data are available from the intermagnet network. we find that the variation in amplitude of the hourly average of h component at low latitude changes from a season to another and it is greater at the maximum solar activity than at the minimum solar activity.keywords: solar cycle 24, season, horizontal component h. | seasonal behavior of h component during solar cycle 24 |
there are several hydrodynamic and magnetohydrodynamic instabilities likely to be at work in the solar tachocline. theoretical models of these instabilities have been developed over the past 25 years, ever since the tachocline was discovered. my primary focus will be on instabilities that arise from rotation and differential rotation, and/or toroidal magnetic fields, and have global scale at least in longitude. i will give a personal perspective on these instabilities, their physical significance, and how they may help determine evidence of magnetic activity we observe at the solar surface. i will also discuss their possible helioseismic signatures, and what they might contribute to the workings of the solar dynamo. a few possible paradoxes will be outlined, as well as how the theories could be made physically more realistic. | tachocline instabilities and solar activity: a fifty-six-year personal perspective |
the zonal flow known as the torsional oscillation has been observed on the sun’s surface since 1980 and in its interior since 1995. it has two branches that migrate during the solar cycle, with one moving towards the equator and the other towards the poles. the rate at which these branches migrate in latitude is tightly correlated with the timing of the solar cycle, as seen during the long minimum between cycles 23 and 24. the poleward branch generally becomes visible 10 to 12 years before the appearance of the magnetic activity associated with the corresponding sunspot cycle as it did for the current cycle 24. however, the poleward flow for cycle 25, which was expected to appear in 2008-2010, was not observed. subsequent analysis showed that it is a very weak flow, and is masked by an apparent change in the background solar differential rotation rate. we will present the latest observations of the zonal flow as determined from global helioseismology, and will discuss the implications for the strength and timing of cycle 25. | temporal evolution of the solar torsional oscillation and implications for cycle 25 |
it has been suggested that the climatic changes during the common era played a critical role in societal reorganizations, including rising and falling of ancient civilizations, human migration and even dynasties alternation in china. since the han dynasty (206 bc- 220 ad), the silk road was one of the most flourished routes connecting the east asia and europe. the silk road along the northern tarim basin gradually declined after a couple of hundred years. it remained unclear what caused the shift in the ancient silk road. here we present high-resolution records from lunnan section (41°13'13″, 84°12'33″), ~5 km from the modern tarim river which fed the ancient oases, to assess the human-environment interactions at 166 bc-702 ad (based on osl age-depth model). three steps of climate change were identified by combining grain size, magnetic susceptibility, elements, and toc along with regional temperature records. at 166bc-60ad, 530-700ad, relatively cool and humid environment was indicated by high em1( coarse fraction of emma extracted by grain size distribution) and ms, coupled with low concentration of elements and toc. at 60-530ad, warm and dry environment was indicated by higher em3(the fine fraction), geochemical elements and toc, which suggested reduced fluvial input. meanwhile, enriched phosphorus (p) content likely resulted from intensified irrigation farming in the eastern han dynasty (25-220ad), which consumed a large fraction of river water and caused decreased river runoff. the climate and environment change in the tarim basin were mainly controlled by westerly-derived precipitation and solar activities. intense human activities in the middle reaches of rivers likely exhausted water resources. | hydrological changes and falling of ancient silk road revealed by tarim river sediments |
three major hypotheses have been proposed to explain the well-known semiannual variation of geomagnetic activity, maxima at equinoxes and minima at solstices. this study examined whether the seasonal variation of equinoctial geomagnetic activity is different in periods of opposite solar magnetic polarity in order to understand the contribution of the interplanetary magnetic field (imf) in the sun-earth connection. solar magnetic polarity is parallel to the earth's polarity in solar minimum years of odd/even cycles but antiparallel in solar minimum years of even/odd cycles. the daily mean of the aa, aa indices during each solar minimum was compared for periods when the solar magnetic polarity remained in opposite dipole conditions. the aa index values were used for each of the three years surrounding the solar minimum years of the 14 solar cycles recorded since 1856. the aa index reflects seasonal variation in geomagnetic activity, which is greater at the equinoxes than at the solstices. the aa index reveals solar magnetic polarity dependency in which the geomagnetic activity is stronger in the antiparallel solar magnetic polarity condition than in the parallel one. the periodicity in semiannual variation of the aa index is stronger in the antiparallel solar polar magnetic field period than in the parallel period. additionally, we suggest the favorable imf condition of the semiannual variation in geomagnetic activity. the orientation of imf toward the sun in spring and away from the sun in fall mainly contributes to the semiannual variation of geomagnetic activity in both antiparallel and parallel solar minimum years. | solar polar magnetic field dependency of geomagnetic activity semiannual variation indicated in the aa index |
the axisymmetric flows, differential rotation and meridional circulation, are essential components of the solar dynamo. we have measured these flows in the surface shear layer for each carrington rotation during solar cycles 23 and 24 (1996-2021) by tracking the motions of the magnetic network seen in magnetograms from soho/mdi and sdo/hmi. we describe several improvements that have been made to our pattern tracking algorithm, including the removal of a systematic shift away from the disc center. weak variations in the differential rotation, known as the torsional oscillation, feature slower flows on the poleward sides of the active latitudes and a high latitude spin-up at cycle maxima. these variations were smaller during the weaker cycle 24. variations in the meridional flow include a slowing of the flow in the active latitudes during cycle maxima, which was more pronounced in cycle 23 than in the weaker cycle 24. furthermore, we find evidence of transient counter-cells at high latitudes which appear seems unrelated to the solar activity cycle. | variations in the suns axisymmetric flows during solar cycles 23 and 24 |
the properties of the solar wind vary with the solar cycle, evolving across time and latitude. the solar wind density, pressure, and speed change with solar activity and affect the overall structure of the heliosphere and characteristics of the heliosheath. many studies have shown the importance of using time-dependent boundary conditions to model the heliosphere (washimi et al. 2011; provornikova et al. 2014; michael et al. 2015). however, these models do not incorporate the effects of solar photoionization of interstellar neutral hydrogen atoms by the solar extreme ultraviolet (euv) flux. it is because the ionization of interstellar neutral hydrogen inside the heliosphere is dominated by charge exchange which accounts for about 76% of the total ionization rate at 1 au, followed by photoionization at about 16% (e.g., sokol et al. 2019). additionally, because the rate of photoionization decreases as 1/r^2, its effect is assumed to be negligible far from the sun. however, gruntman (2015) showed that photoionization could produce appreciable mass loading in the rarified heliosheath where the plasma density is much less than the neutral hydrogen density of the local interstellar medium. we report on the effects of photoionization by a comparison of two 3d magnetohydrodynamic simulations of the heliosphere—one which simulates charge exchange only and one which simulates both charge exchange and photoionization. we use 22-year averaged solar cycle conditions where the solar magnetic field intensity at 1au is varied. we present a detailed comparison of the effect of photoionization on the location of the heliospheric boundaries and the plasma flows in the heliosheath. future work on fully incorporating the solar-cycle-varying solar wind and solar euv flux will be discussed. this project is part of the shield nasa drive science center. | effect of photoionization on the bu global model of the heliosphere |
observations and simulations suggest that thermal wind balance holds to lowest order in the solar convection zone (scz), and an analytic model of solar rotation has been developed by further assuming a functional relationship between the entropy and rotation. below the scz, analytic arguments and simulations have implicated the necessity of a large poloidal field in the deep solar interior for the thin structure of the tachocline. we seek to unify these pictures and find a global equilibrium base state of solar behavior by starting from the exact solution to axisymmetric ideal mhd, the generalized grad-shafranov equation, thereby including magnetic field and poloidal flow from the onset. we find that a tachocline-like structure naturally arises as an equilibrium feature if the poloidal alfvénic mach number approaches unity near the bottom of the scz. flow, a code developed to analyze tokamak equilibrium with arbitrary flow, has been adapted for use in the solar regime and used to examine effects of magnetic field and meridional flow. the next steps include constructing a global equilibrium and establishing linear stability. considering slow perturbations to equilibrium by transport and dissipation provides connections to global solar cycle models (e.g. babcock-leighton dynamos). | towards a global model of equilibrium solar behavior: the tachocline as a trans-alfenic feature |
atmospheric production of 10be is small when solar activity and, therefore, solar magnetic field and total solar irradiance are strong. variations in solar activity affect climate and the production of other climate-relevant isotopes, such as 14c. solar activity is thus an important variable to constrain. since 10be production is clearly related to solar activity and the cycle of beryllium is simpler than that of carbon, 10be records in ice cores have been used to reconstruct total solar irradiance variability. unfortunately, 10be records in ice cores are not only affected by variations in atmospheric production, but are also modulated by changes in wind patterns since spatiotemporal atmospheric 10be gradients are quite large. in that context, sedimentary 10be records from the abyssal ocean could be of great interest: since the residence time of 10be in the ocean is thought to be comparable to the overturning time-scale of the ocean, spatial 10be gradients may be relatively weaker than those in the atmosphere. under these conditions, regional oceanic variability should only weakly affect the distribution of 10be in the ocean and local sedimentary 10be records are expected to represent the global average 10be production better than 10be measured in ice cores. we here show results from a global ocean model of 10be that we use to investigate the spatial variability of simulated sedimentary 10be records and test the sensitivity of the 10be sedimentary flux to uncertainties in the circulation field and in the particle chemistry of beryllium. our ocean model is based on the transport matrix method. the surface 10be input fluxes are taken from atmospheric model simulations. our model experiments, constrained by available dissolved 10be data, show that there exist regions in the ocean where the sedimentary 10be flux is relatively insensitive to changes in input patterns and magnitudes, assumed particle chemistry and flux patterns, and ocean circulation. we submit that sediments records from specific regions, typically located near the centers of oligotrophic gyres, could in principle be used to produce an accurate reconstruction of atmospheric 10be production and thus total solar irradiance. away from these specific regions, however, our model results indicate that sedimentary records could produce reconstructions that could be even more inaccurate than those from ice cores. while our detailed results depend on assumptions about the flux of marine particles and their scavenging behavior, our qualitative conclusions hold over a wide range of parameters. our ability to better constrain the model is limited by the scarcity of available dissolved 10be observations. additional measurements and experiments targeted to constrain the adsorption behavior of be in seawater would help constrain the model further and yield an improved understanding of the marine be cycle. | a model-based evaluation of sedimentary reconstructions of 10be production rates |
estimates of changes in total solar irradiance (tsi) since the pre-industrial period vary widely due to uncertainty in inter-cycle tsi variability, sparse and inaccurate sunspot records before the 20th century, and uncertainty in the relationship between tsi and sunspot proxies. because these sources of error in tsi reconstruction are interdependent, a bayesian hierarchical model is developed to jointly estimate the true values of annual sunspot counts, tsi, and hyperparameters describing measurement errors from satellite tsi observations as well as the nonlinear coupling of tsi and sunspots. daily tsi observations from satellite observation platforms, individual sunspot observations, and magnetic activity proxies, including solar radio flux and the mg ii index, are used to generate the posterior distribution. this analysis provides a range of magnitudes for solar forcing since 1610, which is of critical importance in determining the extent to which a grand minima of solar activity, such as the maunder minimum, may have contributed a large negative radiative forcing effect on earth. an improved record of long-term solar variability and forcing will help distinguish between internal variability and external forcing in generating climate variability. | using bayesian hierarchical modeling of total solar irradiance to estimate uncertainty in solar forcing since the pre-industrial |
the differential rotation is the difference in the rate of rotation of each latitude in the sun indicating that the sun is not a solid body. the differential rotation is the result of the interaction between rotation and convection and causes dynamo circulation that affects the cycle of solar activity. in this research, we measured the coordinates of 304 sunspots umbra as tracer in the rising phase of the solar cycle 24 to obtain the differential rotation equation. coordinates of sunspots were measured using aia images at a wavelength of 4500 å from sdo (solar dynamic observatory) with jhelioviewer software. the areas of sunspots were measured using hmi (helioseismic magnetic imager) images with imagej software. from the measurement, we derived the differential rotation equation and the relation of sidereal rotation and area of sunspots umbra. the differential rotation equation obtained in this research is ω(b) = (14.27 ± 0.01) - (0.78 ± 0.10) sin2b (°/day). there is a difference between the differential rotation equation of the northern and southern hemispheres that indicates the asymmetry between different hemispheres. we got the sidereal rotation of sunspots with area < 5 mh is 0.70% higher than sunspots with area > 15 mh. | the proper motion of sunspots umbra in the rising phase of cycle 24 |
the evolution of solar active regions is closely related to the underlying dynamics of the solar dynamo and magnetic activity cycle. this study explores how information is retained throughout time in active solar regions. we consider a set of solar magnetograms spanning several solar cycles, each magnetogram representing an entire carington rotation. in order to measure the system memory, the mutual information contained in active regions of each magnetogram is calculated. mutual information drops off drastically within the first 20 carington rotations, suggesting a short term memory of about 0.14 solar cycles. mutual information peaked in multiples of 140 carington rotations, which is roughly a solar cycle. long-term memory across multiple solar cycles was explored using conditional mutual information. given the information at a given magnetogram, the additional information shared between the magnetogram a solar cycle prior and a solar cycle ahead was calculated. it is apparent that there is additional information about future solar cycles based not just on the previous solar cycle, but also prior solar cycles. this result is consistent with the hilbert-huang transform of the total information per magnetogram, which shows in weak mode with period of two solar cycles in addition to the strong mode at the period of the solar cycle. finally, we consider whether the memory is scale dependent using a scale dependent filter. | information horizon of magnetic active regions |
we develop an adaptive method to automatically identify ars from radial synoptic maps observed by soho/mdi and sdo/hmi, calibrate the detections between hmi and mdi data based on identified ars flux and area and further derive a homogeneous dataset including ars' area and flux over the last two solar cycles. the data are compared with sunspot number, usaf/noaa sunspot area, smarps and sharps and bard area and flux, which show reasonable agreement. the identified ars during the overlap period of mdi and hmi have the same areas as a whole while the ar flux based on mdi maps is about 1.36 times as large as that of hmi maps. based on our dataset, we find strong ars (|flux| > 1022mx) contribute most to the difference between cycles 23 and 24 while other ars (|flux| < 1022mx) are similar in the two cycles in both area and flux. | automatic detection of solar active regions from soho/mdi and sdo/hmi synoptic magnetograms |
the role of the solar magnetic field in the heliosheath has long been considered passive, but recent studies indicate it may play an active role in collimating the heliosheath plasma into two lobes at high latitudes. we compare results from two mhd models, the bu and moscow models, which treat non-ideal mhd effects differently. the bu model allows for magnetic reconnection at the heliopause between the solar and interstellar magnetic fields, while the moscow model does not allow for direct communication between the solar wind and interstellar medium. we use the same boundary conditions, 22-year averaged solar cycle conditions from 1995 to 2017. an important result is that both models show that the plasma in the heliosheath and heliotail is confined by the solar magnetic field in two lobes. the plasma solutions in the nose of the heliosphere are similar. however, the moscow model displays a long, thousands of au comet-like tail whereas the bu model shows the heliotail is shortened to about 400 au where the interstellar medium flows between the two lobes. the ena maps from the two models show both qualitative and quantitative agreement at ibex energies, despite the different configurations of the heliotail. the modeled ena maps agree qualitatively, but not quantitatively, with ibex ena observations. at higher energies the ena maps from the two models differ, so higher energy ena data (from inca or imap) may be able to determine which model heliotail best fits the data. | a comparison of heliotail configurations arising from different treatments of non-ideal mhd effects with ena maps at ibex energies |
there has been studied a bio-efficiency of geomagnetic variations in the sub-auroral latitudes (yakutsk) in the minimum of the 24th 11-year solar cycle activity (2019) according to the parameters of the solar wind, bz-components of interplanetary magnetic field, solar radiation with a wave length of 10.7 cm. there has been also analyzed a meteo factors' impact (air temperature, air humidity, atmosphere pressure and wind velocity) in the given period. the condition of the cardiovascular system has been estimated daily (march-april of 2019) by a t-wave symmetry coefficient (tsc) in a phase portrait of the ecg. the research has been organized as a part of a simultaneous multi-latitude monitoring "heliomed-2". in the volunteers from sub-auroral latitudes there have not been revealed any disorders of the myocard repolarization in the minimum of the solar activity, according to the tsc in the electrocardiogram phase portrait. cardio-sensitivity (myocard respond to more than 67% of the geomagnetic activity) has not been revealed in the volunteers. the cardiovascular system of the examinees from the sub-auroral latitudes responded only to 45.5% of the geomagnetic variations, most of which was characterized by high parameters of the solar wind dynamic pressure. also, the respond of the myocard of the volunteers has been revealed to change of the atmospheric pressure, while temperature, air humidity and wind velocity did not impact the organism. | the features of the bio-efficiency of geomagnetic activity on the sub-auroral latitiudes in the minimum of the 11-year solar cycle |
the explanation of the observed phenomenon of double peaks of the 11 year sunspot cycles is proposed. the scenario involves five processes of reconstruction of magnetism in the solar convective zone (scz): ω effect, magnetic buoyancy, macroscopic turbulent diamagnetism, rotary \downtriangle ρ effect and meridional circulation. it was established that the reconstruction of magnetism in high-latitude and equatorial domains of the scz occurs in different modes. two time-shifted waves of the toroidal field to the solar surface play a key role in the proposed mechanism in the equatorial domain. | double maxima of 11-year solar cycles |
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