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due to the spherical curvature of the sun, solar observers suffer from an increasing loss of resolution as we move away from the solar equator. thus knowledge of the photospheric flows near the poles has eluded the scope of traditional flow tracking algorithms that are using granules as tracers of the underlying flows.... | tracking supergranulation near the poles with sdo/hmi |
differential rotation and toroidal magnetic bands in the tachocline are unstable to mhd rossby waves and may be responsible for patterns of solar activity seen in the photosphere. helioseismic and surface velocity measurements reveal energetically neutral rossby waves in the supergranulation layer. to explore plausible... | origin of rossby waves observed near the solar surface |
the magnetic power spectrum analysis provides an effective way to understand the observed distribution of the photospheric magnetic fields and their interaction with plasma motions. we aim to investigate the power spectra using spherical harmonic decomposition of soho/mdi and sdo/hmi synoptic magnetograms for cycles 23... | power spectra of the sun's large-scale magnetic field during solar cycles 23 and 24 |
recently bale et al. (2022) have highlighted, using parker solar probe (psp) data close to the sun, the existence of a baseline wind which represents the solar wind whose speed is minimum at a given radial distance. on top of this baseline wind is added a more patchy wind constituted of distinct streams that are organi... | the baseline solar wind |
near one astronomical unit (1 au) and in the outer heliosphere, the solar wind is observed to be a relatively homogeneous and highly turbulent flow that is punctuated occasionally by large-scale transient interplanetary structures such as coronal mass ejections (cmes) and corotating interaction regions (cirs). as the w... | the supergranulation-scale stream structure and underlying acceleration profile of the emerging solar wind |
solar energetic particles (seps) travel along the field lines, scatter by turbulent magnetic field and accelerate by co-rotating interaction regions (cirs), flares and cme-driven shocks. ulyssess observations didn't show any significant change in the density of seps from lower to higher latitudes. possible explanations... | solar energetic particles' transport in the solar wind. |
the first step towards reliable prediction of the impact of solar transients that drive space weather is to accurately model the background solar wind into which these transients propagate. uncertainties in the plasma environment into which cmes propagate can lead to significant errors in time of arrival and impact pre... | modeling solar wind background for cme propagation using the alfven wave solar atmosphere model (awsom) |
ulyesses's observations did not show a significant drop in the density of solar energetic particles from lower to higher latitudes. at the time of ulysses detection, cme shocks were not detected in the data and cir only happens in lower latitudes which led to the theory that the field lines are extending from lower to ... | modeling the effect of photospheric surface flows on the interplanetary magnetic field and propagation of solar energetic particles. |
internetwork (in) magnetic fields can be found inside supergranular cells all over the solar surface. thanks to their abundance and appearance rate, in fields are considered to be an essential contributor to the magnetic flux and energy budget of the solar photosphere, and may also play a major role in the energy budge... | evolution of bipolar internetwork magnetic fields |
it is now well accepted that stellar activity prevents the detection of earth-like planets around solar type stars when using the radial velocity technique. although the impact of dark spots and bright plages, through various processes, is now well modelled, surface flows at different time scales (granulation, supergra... | the impact of surface flows at different scales: exoplanet detectability in radial velocity and high-precision astrometry |
we aim to use the surface flux transport model to simulate the long-term evolution of the photospheric magnetic field from historical observations. in this work we study the accuracy of the model and its sensitivity to uncertainties in its main parameters and the input data. we test the model by running simulations wit... | reconstructing solar magnetic fields from historical observations: testing the surface flux transport model |
the local correlation tracking (lct) technique is a robust method that has been extensively applied to infer proper motions of structures in time series of images. in solar physics research, lct is a useful tool to analyse the dynamics of plasma and the evolution of magnetic fields in the solar atmosphere at different ... | python implementation for local correlation tracking analysis of solar data |
recent studies suggest that the magnetic switchbacks (sbs) detected by the parker solar probe (psp) carry information on the scales of solar supergranulation (large scale) and granulation (medium scale). we test this claim using high-resolution h-alpha images obtained with the visible spectro-polarimeters (vis) of the ... | chromospheric counterpart of the medium-scale solar wind switchbacks |
magnetic field switchbacks are discovered to be ubiquitous in the solar wind using in-situ data from parker solar probe (psp). several scenarios have been proposed in theoretical studies to explain the origin of these switchbacks, among which the small-scale activities in the solar atmosphere are plausible drivers, dir... | statistical study of ejections near corona hole boundaries as possible source of solar wind switchbacks |
magnetic reconnection is understood to have important effects on the dynamics of the solar atmosphere, including those that lead to the formation of the slow solar wind. of particular importance is interchange reconnection between very long "open" field lines emerging from coronal holes into the heliosphere and shorter... | quantifying magnetic reconnection in the solar corona |
the quiet sun may be the biggest laboratory to study physical elementary processes of fundamental importance to space plasma. the advantage is the continuous availability of small-scale events, carrying the hidden microphysics that is responsible for larger-scale phenomena. by small-scale events, we mean spatial dimens... | observations of magnetic evolution and network flares driven by photospheric flows in the quiet sun |
we investigate solar energetic electron transport in a meandering interplanetary magnetic field in the scatter-free regime. the meandering field is adopted from the giacalone 2001 model. the magnetic field is split into an average parker field and a fluctuating field which is due to the photospheric supergranular conve... | propagation of scatter-free energetic electrons in a meandering interplanetary magnetic field |
turbulent convection in stellar envelopes is critical to heat transport and dynamo activity. modeling it well it has proven surprisingly difficult, and recent solar and stellar observations have raised questions about our understanding of the dynamics of both the deep solar convection and the mean structure of the uppe... | supergranulation on the sun and stars: a simple model for its length scale |
the near-surface shear layer (nssl) plays a fundamental role in the structure and dynamics of solar differential rotation and meridional circulation. it is a key to understanding the interaction between convective flows and magnetic fields beneath the visible surface of the sun. to understand the structural and dynamic... | fine structure of near-surface rotational shear layer in 3d radiative hydrodynamics simulations of the solar convection zone |
recent remote observations by suvi, eis, and wispr have shown that small scale dynamics along streamers and separatrix-web (s-web) structures are a crucial driver of the slow solar wind. numerical calculations have shown that magnetic field dynamics at coronal hole boundaries in the middle corona, in particular interch... | what is the width of a slow wind separatrix-web arc in the heliosphere? |
given the emergence of tilted, bipolar active regions, surface flux transport has been shown to reproduce much of the complex evolution of the sun's photospheric magnetic field. surface flux is transported by flows in the surface shear layer - the axisymmetric differential rotation and meridional flow and the non-axisy... | unraveling the complexity of the evolution of the sun's photospheric magnetic field |
we discuss the sources of the solar wind observed by parker solar probe (psp) over its first 12 encounters with the sun, and relate their global properties to those of the embedded turbulence, including characteristics such as overall magnitude, alfvénicity, relative magnitude of density fluctuations, prevalence of swi... | connecting the sun and parker solar probe |
edward w cliver and delores j knipp chart the emergence of solar astonomer avril hart (1928-2011) and her unexpected discovery of a "noisy" velocity field. | avril hart and the discovery of solar supergranulation |
it is often supposed that the convection zones (czs) of low-mass stars are purely adiabatically stratified. this is thought to be because convective motions are extremely efficient at homogenizing entropy within the cz. for a purely adiabatic fluid layer, only very small temperature variations are required to drive con... | the role of rotation in convective heat transport: an application to low-mass stars |
switchbacks are a striking phenomenon in near-sun coronal hole flows, but their origins, evolution and relation to the broadband fluctuations seen farther from the sun are unclear. we aim to determine the scales of variability of switchbacks and, using measurements of the same solar wind stream at two distances, invest... | switchbacks, microstreams and broadband turbulence in the solar wind |
the quiet sun may be the biggest laboratory to study physical elementary processes of fundamental importance to space plasma. the advantage is the continuous availability of small-scale events, carrying the hidden microphysics that is responsible for larger-scale phenomena. by small-scale events, we mean spatial dimens... | network flares and magnetic evolution driven by photospheric flows in the quiet sun |
the solar internetwork contains weak and highly dynamic magnetic fields that are essential to understanding the solar magnetism at small spatial and temporal scales. therefore, it is important to determine how these fields are maintained on the solar surface. using unique hinode observations, we follow the evolution of... | flux appearance and disappearance rates in the solar internetwork |
this poster gives an overview of moore, r. l., tiwari, s. k., panesar, n. k., & sterling, a. c. 2020, apj letters, 902:l35. we propose that the magnetic-flux-rope omega loop that emerges to become any bipolar magnetic region (bmr) is made by a convection cell of the omega-loop's size from initially horizontal magne... | on making magnetic-flux-rope omega loops for solar bipolar magnetic regions of all sizes by convection cells |
one of the most important findings made by parker solar probe (psp) is the omni-presence of the magnetic switchbacks, which are the local backward-bends of the magnetic field lines. although many studies were conducted on the properties and dynamics of these switchbacks, how and where they are generated are still not f... | patches of the magnetic switchbacks: hints of their origins |
context. the study of the dynamic properties of small-scale magnetic fields in the quiet photosphere is important for several reasons: (i) it allows us to characterise the dynamic regime of the magnetic field and points out some aspects that play a key role in turbulent convection processes; (ii) it provides details of... | scaling properties of magnetic field fluctuations in the quiet sun |
rotational suppression of convection can occur on length scales which are larger than a critical length. featherstone & hindman suggest that this can account for a second preferred length-scale in solar convection on supergranule scales. here, i explore if rotational suppression of convection also occurs in the atm... | rotationally constrained convection in the sun: applicable to planetary atmospheres? |
from solar supergranulation to salt flats in bolivia, from veins on leaves to cells on drosophila wing disks, polygon-based networks exhibit great complexities, yet similarities and consistent patterns emerge. based on analysis of 99 polygonal tessellations with a wide variety of physical origins, this work demonstrate... | e2 and gamma distributions in polygonal networks |
from impulsive events to quasi-stable structures, small-scale magnetic fields are ubiquitous in the quiet solar atmosphere and dominate its structure and dynamics. the processes and timescales that underpin their evolutionary characteristics depend on their size; the smaller the structures the faster they evolve. their... | the many faces of small-scale solar magnetic features |
it is well-known that there is a close relationship between the supergranules, magnetic field and the extreme-ultraviolet (euv) network of the solar atmosphere. we have obtained the network characteristics from the imaging data from the atmospheric imaging assembly (aia) on board the solar dynamics observatory (sdo) in... | solar cycle variations of the euv network characteristics from sdo/aia |
we study the temperature profile of the solar chromosphere by combining the information from an empirical model of the chromosphere, a theoretical chromospheric heating model, and a theoretical radiation model. with the observed temperature minimum at z=650km, the temperature decreases with increasing altitude up to th... | understanding of the temperature profile of the solar chromosphere |
the pixel-to-pixel (p2p) artifact, which occurs due to the discrete nature of matrix receivers, sets an independent frequency standard. for this reason, this effect can be used to study the differential rotation of the sun based on tracers such as solar faculae. the results are in good agreement with ground-based obser... | differential rotation of the sun, helioseismology data, and estimation of the depth of superconvection cells |
the distribution of magnetic fields on the solar surface and magnetic flux transport are controlled by surface and subsurface plasma flows. thus, understanding the links between the flow dynamics and global magnetic fields is potentially important for predicting the flux evolution and estimating the structure of the co... | links between global solar magnetic fields and subsurface flows |
helioseismology is a valuable tool which has allowed us to better understand the sun's internal structure and dynamics. time-distance helioseismology, in particular, has been used extensively to study the subsurface flow structure around localized solar features like supergranulation and sunspots. however, the applicab... | time-distance helioseismology: testing the state-of-the art for investigating the structure of sunspots and supergranulation |
the emergence of magnetic field from the interior of the sun generates a poloidal magnetic field from rising toroidal magnetic field. solar active regions and sunspots are the strongest concentrations of magnetic field on the surface, and how they emerge is a crucial, but poorly understood aspect of the solar dynamo. o... | importance of convection for emerging active regions on the sun |
in the solar atmosphere, the jets are ubiquitous and found to be at various spatia-temporal scales. they are significant to understand energy and mass transport in the solar atmosphere. recently, the high-speed transition region jets are reported from the observation. here we conduct a numerical simulation to investiga... | origin of both the fast hot jet and the slow cool jet from magnetic flux emergence and advection in the solar transition region |
solar energetic particles (seps) are accelerated by solar flares or by coronal mass ejection shock waves in the corona. most of the particles we detected at 1 au are released through open magnetic field lines to interplanetary space. therefore, the configuration of coronal magnetic fields during an sep event is crucial... | propagation of solar energetic particles in coronal magnetic fields |
the fast solar wind that fills the heliosphere originates from regions of open magnetic field on the sun called 'coronal holes', driven by the pressure drop between the solar surface and the interstellar medium. the magnetic field near the solar surface within coronal holes is structured on angular scales associated wi... | interchange reconnection within coronal holes powers the solar wind |
thermal convection is the dominant mechanism of energy transport in the outer envelope of the sun (one-third by radius). it drives global fluid circulations and magnetic fields observed on the solar surface. convection excites a broadband spectrum of acoustic waves that propagate within the interior and set up modal re... | seismic sounding of convection in the sun |
the heating of the solar wind from open-field regions in the corona is the subject of an ongoing body of work in the solar physics community. we present recent progress to understand the role of alfvén-wave-driven turbulence in flux tubes open to the heliosphere. our models use three-dimensional, time-dependent forms o... | magnetic influences on turbulent heating and jet production in coronal holes |
we present measurements from the fields, sweap, and isois instruments on parker solar probe (psp), combined with pfss modeling of the magnetic field in the low corona. our data shows that the solar wind proton and alpha velocity spectra and the alpha particle abundance are modulated on angular scales associated with th... | interchange reconnection within coronal holes powers the fast solarwind: suprathermal ion flows and bursty magnetic fields modulated by the network magnetic field. |
the fluctuation spectra of solar active regions (ars) contain information about the geometrical features and ground physical processes responsible for the appearance of such a background vibration noise. the investigation is based on an analysis of a time series built photospheric magnetograms and comprises case studie... | long period fluctuations of solar active regions |
the chromospheric network, the bright emission network seen in the chromospheric lines such as ca ii k and hα, outline the supergranulation cells. the ca images are dominated by the chromospheric network and plages which are good indicators of solar activity. further, the ca line is a good proxy to the uv irradiance wh... | studies of synoptic solar activity using kodaikanal ca k data |
the best-studied star the sun still harbors mysteries for scientists to puzzle over. a new study has now explored the role of tiny magnetic-field hiccups in an effort to explain the strangely high temperatures of the suns upper atmosphere.schematic illustrating the temperatures in different layers of the sun. [esa]stra... | heating the chromosphere in the quiet sun |
the dynamics of solar and interplanetary plasmas is governed by coherent structures such as current sheets and magnetic flux ropes which are responsible for the genesis of intermittent turbulence via magnetic reconnections in solar supergranular junctions, solar coronal loops, the shock-sheath region of an interplaneta... | solar and interplanetary turbulence: lagrangian coherent structures |
the multiscale structure of solar convection plays a key role in the local and global dynamics of the sun and the interaction of flows with magnetic fields. we study the spatiotemporal structure of subphotospheric convection using the full-disk horizontal-velocity maps obtained from the helioseismic and magnetic imager... | detection of giant-scale convection in the near-surface shear layer of the sun |
we present measurements of the sun's sub-surface convective flows and provide evidence that the pattern of supergranulation is driven at the surface. the pattern subsequently descends slowly throughout the near-surface shear layer in a manner that is inconsistent with a 3-d cellular structure. the flow measurements are... | helioseismic imaging of supergranulation throughout the sun's near-surface shear layer |
solar supergranulation has been characterized as horizontally divergent flow motions having a typical scale of 32 mm using doppler imaging, granule tracking and helioseismology. unlike granules, the size of which is comparable to both the thickness of the radiative boundary layer and local scale height at the photosphe... | supergranulation as the sun's largest buoyantly driven mode of convection |
recent observations and models have raised questions about our understanding of the dynamics of the deep solar convection. in particular, the amplitude of low wavenumber convective motions appears to be too high in both local area radiative magnetohydrodynamic and global spherical shell magnetohydrodynamic simulations.... | the amplitude of the deep solar convection and the origin of the solar supergranulation |
internetwork (in) magnetic fields are highly dynamic, short-lived magnetic structures that populate the interior of supergranular cells. since they are spread all over the sun, they may hold a significant fraction of the total magnetic energy stored in the photosphere. therefore, it is crucial to understand their role ... | emergence of internetwork magnetic fields into the chromosphere and transition region |
small-scale internetwork (in) magnetic fields are considered to be the main building blocks of the quiet sun magnetism. it is therefore of paramount importance to understand how these fields are generated on the solar surface. to shed new light on this open question, we studied the appearance modes and spatio-temporal ... | unipolar versus bipolar internetwork flux appearance |
internetwork (in) magnetic fields are highly dynamic, short-lived magnetic structures that populate the interior of supergranular cells. since they emerge all over the sun, these small-scale fields bring a substantial amount of flux, and therefore energy, to the solar surface. because of this, in fields are crucial for... | emergence of internetwork magnetic fields through the solar atmosphere |
whereas the average interplanetary magnetic field near earth commonly aligns with the parker spiral in non-transient solar wind, the instantaneous field direction does not, indicating that field lines wander about the spiral direction. the scale-length of that wandering carries information about parallel fluctuations o... | using ace-earth magnetic connection events to estimate length-scales of field line wandering with respect to the parker spiral |
energetic particles in the inner heliosphere are accelerated at a variety sources such as co-rotating interaction regions (cirs), flares and cme-driven shocks. they propagate to 1 au along interplanetary magnetic field, experiencing scattering by turbulent magnetic field along their way. recently ulysses observations o... | particle transport in the solar wind |
solar supergranules remain a mysterious phenomenon, half a century after their discovery. one particularly interesting aspect of supergranulation is its wave-like nature detected in fourier space. using sdo/hmi local helioseismology and granulation tracking, we provide new evidence for supergranular waves. we also disc... | supergranular waves revisited |
since the year 2010, sdo is sending more than a terabyte of solar observations per day. by offering such an unprecedented large and varied data sets, this mission has propelled the solar physics community into the era of "big data" analytics. as an answer to this new technical and scientific challenge, we present here ... | tracking algorithms and machine learning for the characterization of active regions over the solar cycle 24 |
recent work on modeling solar photospheric flows has replaced those based on random-walks with kinematic models based upon observed convective properties. these models have successfully reproduced many aspects of the solar cycle. here we present a dynamic model of surface flows based upon simplified mhd driven by super... | a simplfied mhd model of solar surface flows |
the mechanism behind filament-channel formation is a longstanding mystery, while that underlying the initiation of coronal mass ejections and jets has been studied intensively but is not yet firmly established. in previous work, we and collaborators have investigated separately the consequences of magnetic-helicity con... | filament channel formation, eruption, and jet generation |
our understanding of the interior dynamics that give rise to a stellar dynamo draws heavily from investigations of similar dynamics in the solar context. unfortunately, an outstanding gap persists in solar dynamo theory. convection, an indispensable component of the dynamo, occurs in the midst of rotation, and yet we k... | stellar ro |
we apply helioseismic holography to hmi observations of several hundred of the largest active regions and assess the inferred flows averaged after spatially aligning active regions selected in several ranges of magnetic flux. this ensemble averaging helps greatly reduce the dominating effect of the supergranulation sig... | helioseismic holography of flows around the averaged active region |
in the solar atmosphere, the jets are ubiquitous and found to be at various spatia-temporal scales. they are significant to understand energy and mass transport in the solar atmosphere. recently, the high-speed transition region jets are reported from the observation. here we conduct a numerical simulation to investiga... | origin of the high-speed jets fom magnetic flux emergence in the solar transition region as well as their mass and energy contribuctions to the solar wind |
local time-distance helioseismology and magnetic field measurements from the hmi instrument on sdo provide unique high-resolution data that allow us to investigate detailed dynamics of the upper convection zone and its relation to the magnetic field evolution during the first five years of the current solar cycle. this... | relationship between subsurface flows and magnetic field evolution in solar cycle 24 |
solar eruptive events ranging from small-scale jets to global-scale coronal mass ejections are associated with filaments and their underlying filament-channel magnetic structures. in previous work, we have demonstrated that sheared-arcade filament channels can be formed via the process of helicity condensation. magneti... | multiscale helicity condensation and filament channel formation |
we have developed a surface flux transport simulation utilizing a semi-lagrangian scheme to advect discrete magnetic flux elements. advection occurs due to the flow fields from supergranulation, meridional flow, and differential rotation. granular advection is modeled using a time integrated effect which lowers the com... | a 2d discrete surface flux transport (dsft) model applied to polar and quiet sun regions. |
travel times are normally measured between pairs of points in the solar photosphere by making temporal cross correlations of a signal (e.g. doppler line shift) and detecting the systematic signatures in the correlation. normally the solar wave field is directionally isotropic and the pair of points is most sensitive to... | systematic and s/n improvements in time-distance helioseismology from azimuthal filtering |
local helioseismology and magnetic field measurements from the hmi instrument on sdo provide unique high-resolution data that allow us to investigate detailed dynamics of the upper convection zone and its relation to the magnetic field evolution during the first five years of the current solar cycle. this study is focu... | solar-cycle evolution of subsurface flows and magnetic field |
i study the complexity of supergranular cells using intensity patterns from kodaikanal solar observatory. the chaotic and turbulent aspect of the solar supergranulation can be studied by examining the interrelationships amongst the parameters characterizing supergranular cells namely size, horizontal flow field, lifeti... | supergranular parameters |
these tables give the azimuthally averaged horizontal velocity components vr and vt for the average supergranular outflows and inflows at various latitudes, as displayed for 40° latitude in fig. 13 in the paper. the velocities have been computed by the method of local correlation tracking using intensity images from th... | vizier online data catalog: solar supergranular velocity profiles (langfellner+, 2015) |
the enhanced resolution provided by iris has allowed for the direct observation of small-scale features in the chromosphere and transition region. one feature identified in iris observations is jet-like emission from bright network patches. in this project, we compare the network jets presented by tian et al. (2014, sc... | an investigation of magnetic thresholds for the production of iris network jets |
plasma from the sun known as the slow solar wind has been observed far away from where scientists thought it was produced. now new simulations may have resolved the puzzle of where the slow solar wind comes from and how it escapes the sun to travel through our solar system.an origin puzzlea full view of a coronal hole ... | escape for the slow solar wind |
the heliosphere is permeated with highly structured solar wind originating from the sun. one of the primary science objectives of parker solar probe (psp) is to determine the structures and dynamics of the plasma and magnetic fields at the sources of the solar wind. however, establishing the connection between in situ ... | in situ remnants of solar surface structures from jensen-shannon scalogram |
the lifetimes and length-scales for supergranular cells in active and quiescent regions of the solar chromosphere, and the relation between the two, were studied using a time series of ca ii k filtergrams. the lifetimes, in contrast to supergranular length scale and fractal dimension, show no significant dependence on ... | dependence of solar supergranular lifetime on surface magnetic activity and rotation |
switchbacks are a striking phenomenon in near-sun coronal hole flows, but their origins, evolution, and relation to the broadband fluctuations seen farther from the sun are unclear. we use the near-radial lineup of solar orbiter and parker solar probe during september 2020 when both spacecraft were in wind from the sun... | switchbacks, microstreams, and broadband turbulence in the solar wind |
supergranule aggregation, i.e., the gradual aggregation of convection cells to horizontally extended networks of flow structures, is a unique feature of constant heat flux-driven turbulent convection. in the present study, we address the question if this mechanism of self-organisation of the flow is present for any flu... | supergranule aggregation: a prandtl number-independent feature of constant heat flux-driven convection flows |
the solar active region (ar), noaa 12192, appeared in 2014 october as the largest ar in 24 years. here we examine the counterintuitive nature of two diffusion-driven processes in the region: the role of helicity buildup in the formation of a major filament, and the relationship between the effects of supergranular diff... | the great solar active region noaa 12192: helicity transport, filament formation, and impact on the polar field |
magnetic active regions on the sun are harbingers of space weather. understanding the physics of how they form and evolve will improve space weather forecasting. our aim is to characterise the surface magnetic field and flows for a sample of active regions with persistent magnetic bipoles prior to emergence. we identif... | evolution of the magnetic field and flows of solar active regions with persistent magnetic bipoles before emergence |
the network structure seen in the solar images is the outline of supergranulation, which is the large-scale convection in the sun with a size of about 30 mm and a lifetime of 24 hr. we have obtained the supergranulation lane widths from the autocorrelation function of image windows from the ca ii k spectroheliograms. t... | correlation between supergranular lane widths and sunspot number; a simple way to predict the amplitude of sunspot cycle |
direct seismic imaging of subsurface flow, sound speed, and magnetic field is crucial for predicting flux-tube emergence on the solar surface, an important ingredient for space weather. the sensitivity of helioseismic mode-amplitude cross-correlation to p- and f-mode oscillations enables formal inversion of such subpho... | recipe for inferring subsurface solar magnetism via local mode coupling using slepian basis functions |
context. extreme ultraviolet (euv) observations of the quiet solar atmosphere reveal extended regions of weak emission compared to the ambient quiescent corona. the magnetic nature of these coronal features is not well understood.aims: we study the magnetic properties of the weakly emitting extended regions, which we n... | coronal voids and their magnetic nature |
we investigate which scalar quantity or quantities can best predict the loss of equilibrium and subsequent eruption of magnetic flux ropes in the solar corona. our models are initialized with a potential magnetic arcade, which is then evolved by means of two effects on the lower boundary: first, a gradual shearing of t... | eruptivity criteria for solar coronal flux ropes in magnetohydrodynamic and magnetofrictional models |
we use cosmological adaptive mesh refinement code enzo zoom-in simulations to study the long-term evolution of the collapsing gas within dark matter haloes at z. this direct collapse process is a leading candidate for rapid formation of supermassive black hole (smbh) seeds. to circumvent the courant condition at small ... | supermassive black hole seed formation at high redshifts: long-term evolution of the direct collapse |
the observed burst duration and energies of the neutrinos from supernova 1987a strongly limit the possibility of any weakly-interacting light particle species being produced in the proto-neutron star (pns) core and leading to efficient energy loss. we reexamine this constraint on weinberg's higgs portal model, in which... | supernovae and weinberg's higgs portal dark radiation and dark matter |
we study in detail the collider signatures of an su(2) rfermionic quintuplet in the framework of left-right symmetric model in the context of the 13 tev lhc. apart from giving a viable dark matter candidate ( χ 0), this model provides unique collider imprints in the form of same-sign multileptons through the decays of ... | same-sign multilepton signatures of an su(2) rquintuplet at the lhc |
we calculate the cross sections of atomic ionization by absorption of scalar particles in the energy range from a few ev to 100 kev. we consider both nonrelativistic particles (dark matter candidates) and relativistic particles that may be produced inside the sun. we provide numerical results for atoms relevant for dir... | atomic ionization by scalar dark matter and solar scalars |
the qcd axion and an axion-like particle (alp) are compelling candidates of dark matter. for the qcd axion, it is known that when the peccei-quinn (pq) symmetry is spontaneously broken after inflation, the large initial fluctuation can lead to axion clump formation. on the other hand, when the symmetry is already broke... | can axion clumps be formed in a pre-inflationary scenario? |
one of the challenging questions in cosmology is the nature of dark matter particles. fuzzy dark matter (fdm) is one of the candidates which is made of very light (mfdm≃10-22- 10-21 ev ) bosonic particles with no self-interaction. it is introduced by the motivation to solve the core-cusp problem in the galactic halos. ... | investigation of two colliding solitonic cores in fuzzy dark matter models |
axionlike particles (alps) are promising dark matter candidates. they are typically described by a classical field, motivated by large phase space occupation numbers. here we show that such a description is accompanied by a quantum effect: squeezing due to gravitational self-interactions. for a typical qcd axion today,... | nonclassicality of axionlike dark matter through gravitational self-interactions |
we discuss singlet fermion dark matter within a left-right symmetric model promoting baryon and lepton numbers as separate gauge symmetries. we add a simple dirac fermionic dark matter singlet under su(2) l , r with nonzero and equal baryon and lepton number which ensures electric charge neutrality. such a dark matter ... | singlet fermion dark matter within left-right model |
we study the collider phenomenology of non minimal universal extra dimensional (nmued) model in the context of the large hadron collider at cern. nmued is an incarnation of the standard model in 4 + 1 space-time dimensions compactified on an s 1/ z 2 orbifold supplemented with boundary localized operators with unknown ... | exploring non minimal universal extra dimensional model at the lhc |
this article gives an overview on the status of experimental searches for dark matter at the end of 2014. the main focus is on direct searches for weakly interacting massive particles (wimps) using underground-based low-background detectors, especially on the new results published in 2014. wimps are excellent dark matt... | dark matter 2014 |
we consider an extension to the standard model (sm) with two extra real singlet scalars which interact with the sm higgs particle. the lighter scalar is taken as the dark matter (dm) candidate. we show that the model successfully explains the relic abundance of the dm in the universe and evades the strong bounds from d... | hierarchy problem and the vacuum stability in two-scalar dark matter model |
dark matter (dm) detection prospects at future colliders are reviewed under the assumption that dm particles are fermions of the majorana or dirac type. although the discussion is quite general, one will keep in mind the recently proposed candidate based on an excess of energetic photons observed in the center of our g... | searching for dark matter at colliders |
scintillators are widely used as particle detectors in particle physics. scintillation at cryogenic temperatures can give rise to detectors with particle discrimination for rare-event searches such as dark matter detection. we present time-resolved scintillation studies of cesium iodide (csi) under excitation of both α... | particle detection at cryogenic temperatures with undoped csi |
we identify the parameter regions of the phenomenological minimal supersymmetric standard model (pmssm) with the minimal possible fine-tuning. we show that the fine-tuning of the pmssm is not large, nor under pressure by lhc searches. low sbottom, stop and gluino masses turn out to be less relevant for low fine-tuning ... | supersymmetry with dark matter is still natural |
in this conference, i have talked about two scenarios in which the out-of-equilibrium production of dark matter (dm) particles in the early universe is unavoidable. in the first one \cite{bhattacharyya_freezing-dark_2018}, we extend the standard model (sm) of particle physics by an extra $u(1)$ gauge group under which ... | freeze-in production of dark matter through spin-1 and spin-2 portals |
we study a left right (lr) extension of the standard model (sm) where the dark matter(dm) candidate is composed of a set of fermionic majorana triplets. the dm is stabilized by a remnant z2 symmetry from the breaking of the lr group to the sm. two simple scenarios where the dm particles plus a certain set of extra fiel... | fermionic triplet dark matter in an s o (10 )-inspired left-right model |
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