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rossby waves play a fundamental role in angular momentum processes in rotating fluids. in addition to the potential to shed light on physical mechanisms operating in the solar convection zone, the recent detection of rossby waves in the sun (löptien et al. 2018; liang et al. 2018) also serves as a means of comparison b... | detection of rossby waves in the sun using normal-mode coupling |
recent measurements suggest that a portion of the earth's core may be stably stratified. if this is the case, then the earth's core joins the many planetary and stellar objects which have a stably stratified region adjacent to a convective region. the stably stratified region admits internal gravity waves which can tra... | internal wave generation by turbulent convection |
one of the most interesting aims for the study of exoplanets to understand under which conditions life could appear and survive in other environments. to be able to bear any form of life, "environments must provide extended regions of liquid water, conditions favorable for the assembly of complex organic molecules, and... | assessing the habitability of observed super earths |
recent progress in the ab-initio modeling of solar magnetoconvection makes it possible to simulate the surface dynamics of solar-type stars with a high degree of realism. these simulations can be used to characterize stellar photospheric disturbances which contaminate the radial velocity signal and limit our capabiliti... | characterization of stellar jitter using 3d realistic modeling of solar-type stars |
τ ceti, a g8-v class star, has similar physical properties with our sun, even though most values are smaller and not as active as the sun. it has also been widely reviewed that this metal-poor population ii star has terrestrial planetary systems, some of which are in the habitable zone. this paper aims to build the int... | interior structure of solar-like star τ ceti |
r coronae borealis (rcb) stars are rare yellow supergiant type stars with peculiar surface compositions thought to form from the merger of two white dwarfs. many attempts have been made to model these stars in order to reproduce their lifetimes and surface compositions. using the 1d stellar evolution code, mesa, we var... | improved r coronae borealis simulations: simulating r coronae borealis evolution with large-scale nucleosynthesis post-processing |
over 4000 exoplanets have been discovered in the past 25 years, most of which orbit around low-mass stars. for the shortest period exoplanets, like hot-jupiter systems, star-planet tidal interactions are likely to have played a major role in the orbital architecture and rotational evolution of the planets and their hos... | effect of differential rotation on tidal waves in the convective envelope of low-mass stars and giant planets |
we use full-disk, soho/eit 195 $å$ calibrated images to measure latitudinal and day to day variations of area and average photon fluxes of the near equatorial coronal holes. in addition, energy emitted by the coronal holes with their temperature and strength of magnetic field structures are estimated. by analyzing data... | thermal and magnetic field structure of near equatorial coronal holes |
tidal interactions are important in driving spin and orbital evolution in various astrophysical systems such as hot jupiters, close binary stars and planetary satellites. however, the fluid dynamical mechanisms responsible for tidal dissipation in giant planets and stars remain poorly understood. one key mechanism is t... | convective turbulent viscosity acting on equilibrium tidal flows: new frequency scaling of the effective viscosity |
the development of astronomical observations of various objects in 20th century has revealed that the universe is full of explosions (flares or bursts) and plasma outflows such as high-speed jets. why is our universe filled with such extraordinary activity? when i started astrophysical research in 1977, i was fascinate... | from jets to superflares: extraordinary activity of magnetized plasmas in the universe |
testing oxygen opacity calculations is important for understanding the sun and white dwarf stars. near the solar convection zone base, te~180 ev, ne ~9e22 electrons/cc, and oxygen is mostly h-like or fully-stripped. highly-ionized oxygen produces a relatively simple opacity spectrum, but its calculation relies on untes... | oxygen opacity experiments for stellar interiors. |
in many planetary systems, the host star will expand during post-main-sequence evolution to engulf close-orbiting planets and/or brown dwarfs (hereafter substellar bodies, sbs). substellar engulfment stands as a possible explanation to stellar remnants with close-orbiting sb, evolved stars with unusually high surface a... | the hydrodynamics of planetary engulfment |
a polytrope with index n = 1.5 is a good model for fully convective star cores like red giants, brown dwarfs, giant gaseous planets (like jupiter), while a polytrope with index n = 3.0 is usually also used to model main-sequence stars like our sun, at least in the radiation zone, corresponding to the eddington standard... | radial pulsations of distorted polytropes of non-uniform density |
modeling of stars, more massive than the sun, with shallow convection zones opens an opportunity to investigate their turbulent dynamics in great detail, from non-linear self-organization of multiscale convection patterns to mechanisms of acoustic wave excitation near the photosphere and interface between the radiative... | turbulent dynamics of main-sequence stars with shallow outer convection zones revealed in 3d radiative hydrodynamics simulations |
context. a new, self-consistent, scale-free theory of stellar convection was recently developed (sfct) in which velocities, dimensions, and energy fluxes carried by the convective elements are defined in a rest frame co-moving with the convective element itself. as the dynamics of the problem is formulated in a differe... | the scale-free theory of stellar convection. a critical review and new results |
reliable models of convection are critical to interpreting the high-quality stellar data produced by state-of-the-art missions such as kepler, tess, and soon plato. the depth of convective overshooting and the amount of mixing that takes place in the overshooting layer are major open questions for modeling stars. model... | overshooting, filling factors, and plume dynamics: the shape of compressible convection in the deep interior of stars |
we analyze data for 55 solar analogs which are characterized by significant scatter of lithium abundance in their atmospheres. among these stars there are 22 solar twins. preliminary analysis of the tess mission data allowed us to reveal rotation modulation of stellar brightness associated with starspots. for some of o... | activity of solar twins |
the rotation-activity relation of m dwarfs is of high astrophysicalinterest due to (i) the predicted dynamo transition at the fullyconvective boundary (spt ~ m3), (ii) differences in angular momentumloss with respect to solar-type stars, and (iii) the small radii oftheir planets' habitable zones where they are strongly... | spin-down, dynamos, and habitability: xmm and k2 exploration of nearby m dwarfs |
a dramatic increase in observational data from nasa's kepler, k2, and tess missions and supporting ground-based observatories have opened new opportunities to investigate the internal structure, dynamics, and evolution of stars and their atmospheres. we present 3d radiative mhd simulations for several main-sequence sta... | dynamics and structure of main-sequence stars with shallow convection zones |
we explore how thermal rossby waves propagate within the gravitationally stratified atmosphere of the sun's convective zone. under the conditions of rotationally constrained dynamics, we derive a local dispersion relation for atmospheric waves in a fully compressible stratified fluid. this dispersion relation describes... | radial trapping of thermal rossby waves within the sun's convection zone |
we conduct one-dimensional stellar evolution simulations of red supergiant (rsg) stars that mimic common envelope evolution (cee) and find that the inner boundary of the envelope convective zone moves into the initial envelope radiative zone. the envelope convection practically disappears only when the rsg radius decre... | the depletion of the red supergiant envelope radiative zone during common envelope evolution |
it was recently claimed that the sun's photometric variability is abnormally low relative to analogous stars observed by nasa's kepler space telescope to rotate every 20-30 days. the implication is that the sun's various manifestations of magnetic activity could likewise exhibit much higher excursions in the future or ... | the photometric variability and chromospheric emission of kepler's solar-aged solar analogs are consistent with the modern sun |
two mechanisms are often invoked to explain tidal friction in binary systems. the ``dynamical tide” is the resonant excitation of internal gravity waves by the tide, and their subsequent damping by nonlinear fluid processes or thermal diffusion. the ``equilibrium tide” refers to non-resonant excitation of fluid motion ... | orbital decay in binaries with evolved stars |
we present the first detailed three-dimensional hydrodynamic implicit large eddy simulations of turbulent convection for carbon burning. the simulations start with an initial radial profile mapped from a carbon burning shell within a 15 m⊙ stellar evolution model. we considered 4 resolutions from 1283 to 10243 zones. t... | the first 3d simulations of carbon burning in a massive star |
the connection between nuclear fusion in the sun's core and solar irradiance is obscured among other things by uncertainty over the mechanism of coronal heating. data for solar wind density and velocity, sunspot number, and euv flux suggest that electromagnetic energy from the sun's convection zone is converted by indu... | the solar chromosphere as induction disk and the inverse joule-thomson effect |
key physical ingredients governing the evolution of massive stars are mass losses, convection and mixing in radiative zones. these effects are important both in the frame of single and close binary evolution. the present paper addresses two points: 1) the differences between two families of rotating models, i.e. the fa... | physics of massive stars relevant for the modeling of wolf-rayet populations |
the internal rotation of low mass stars all along their evolution is of primary interest when studying their rotational dynamics, internal mixing and magnetic fields generation. in this context, helio- and asteroseismology probe angular velocity gradients deep within solar type stars. still the rotation of the close ce... | 2d dynamics of the radiation zone of low mass stars |
recent observational modelling of the atmospheres of hydrogen-free wolf-rayet stars have indicated that their stellar surfaces are cooler than those predicted by the latest stellar evolution models. we have created a large grid of pure helium star models to investigate the dependence of the surface temperatures on fact... | helium stars: towards an understanding of wolf-rayet evolution |
the sun's deep-seated convective flows must ultimately sustain not just the efficient emf from which solar magnetism derives, but also the large-scale shearing and circulatory flows thought to imbue that magnetism with its remarkable spatiotemporal ordering. exploration of the dynamo process ultimately requires knowled... | numerical simulation of a laboratory star |
the sun is the most studied of stars and a laboratory of fundamental physics. however, the understanding of our star is stained by the solar modelling problem which can stem from various causes. we combine inversions of sound speed, an entropy proxy and the ledoux discriminant with the position of the base of the conve... | combining multiple structural inversions to constrain the solar modelling problem |
to interpret the high-quality data produced from recent space-missions it is necessary to develop theoretical and computational modeling of convection under realistic stellar conditions. we use the multi-dimensional, time implicit, fully compressible, hydrodynamic, implicit large-eddy simulation code music, to study th... | modeling stars in different dimensions: a comparison of overshooting in 2d and 3d simulations |
gravito-inertial waves can be excited at the interface of convective and radiative regions and by the reynolds stresses in the bulk of the convection zone. the magnitude of their energy flux will therefore vary with the properties of the convection. to assess how convection changes with rotation, a simplified local mon... | rotating convection and gravito-inertial wave generation in stellar interiors |
the kepler satellite has provided a revolution in understanding not just in the field of exoplanets but also in the field of stellar pulsation. while great strides have been made in the seismology of red giants and solar-like stars, equally significant progress has been made in the observations of white dwarf (wd) star... | seismologically mining white dwarfs in the k2 archive for their rotation rates, convection properties, and chemical profiles |
main-sequence stars with masses less than 30% that of the sun are fully convective and are the most abundant stars in the galaxy. the question of how fully convective stars generate their magnetic field is of intrinsic interest and also bears upon the habitability of their orbiting planets. these stars currently provid... | flare statistics and high resolution spectroscopy of a volume complete sample of mid-to-late m dwarfs within 15 parsecs |
semidiurnal atmospheric thermal tides are important for terrestrial exoplanets in the habitable zone of their host stars. with solid tides, they torque these planets, thus contributing to determine their rotation states as well as their climate. given the complex dynamics of thermal tides, analytical models are essenti... | repercussions of thermal atmospheric tides on the rotation of terrestrial planets in the habitable zone |
in g dwarfs, the surface distribution, coverage and lifetimes of starspots deviate from solar-like patterns as the rotation rate increases. we set up a numerical platform which includes the large-scale rotational and surface flow effects, aiming to simulate evolving surface patterns over an activity cycle for up to 8 t... | activity variation driven by flux emergence and transport on sun-like stars |
helicity (velocity-vorticity correlation) represents some structural information of turbulence. by assuming homogeneous isotropic and non-mirror-symmetric property for the basic fields (the lowest-order fields in a derivative expansion formulation), the reynolds-stress expression is derived from the fundamental equatio... | inhomogeneous helicity effects in angular-momentum transport in geophysical and astrophysical turbulent flows |
highly stratified convection is ubiquitous among natural systems including planetary atmospheres and stellar envelopes. here we study fully compressible convection within plane-parallel, polytropically stratified layers using the dedalus pseudospectral framework at moderate to high rayleigh number. we find that large s... | sustained shear flows in stratified convection |
a significant source of uncertainty in modeling the progenitor systems of type ia supernovae is the dynamics of the convective urca process in which beta decay and electron capture reactions remove energy from and decrease the buoyancy of carbon-fueled convection in the progenitor white dwarf. the details of the urca p... | three-dimensional simulations of the convective urca process in pre-supernova white dwarfs |
how the volatile content influences the primordial surface conditions of terrestrial planets and, thus, their future geodynamic evolution is an important question to answer. we simulate the secular convective cooling of a 1-d magma ocean (mo) in interaction with its outgassed atmosphere. a first rapid cooling stage, wh... | the relative influence of h2o and co2 on the primitive surface conditions of venus |
we present an updated view of the rotation-activity-age relation for (old) field m dwarfs based on k2 rotation periods and flares,archival x-ray and uv data,and dedicated chandra and xmm-newton observations.the rotation-activity-age relation can be used as a proxy for magnetic fields- which are difficult to measure in ... | a path towards understanding the rotation-activity-age relation of m dwarfs with k2 mission, x-ray and uv data |
a simplified monomodal model for stellar and planetary convection is derived for the magnitude of the rms velocity, degree of superadiabaticity, and characteristic length scale as a function of rotation rate as well as with thermal and viscous diffusivities, utilizing a heat-flux maximization principle and a spectrally... | a model of rotating convection in stellar interiors |
the development of astronomical observations of various objects in 20th century has revealed that the universe is full of explosions (flares or bursts) and plasma outflows such as high-speed jets. why is our universe filled with such extraordinary activity? when i started astrophysical research in 1977, i was fascinate... | from jets to superflares: extraordinary activity of magnetized plasmas in the universe |
we have recently computed a grid of 3d radiation-hydrodynamical simulations for the atmosphere of 70 pure-hydrogen da white dwarfs in the range 7.0 < log g < 9.0. this includes the full zz ceti instability strip where da white dwarfs are pulsating, by far the most common type of degenerate pulsators. we have sign... | new insights on pulsating white dwarfs from 3d radiation-hydrodynamical simulations |
in this talk, we present recent investigations of the convection, oblateness and differential rota-tion in rapidly rotating late-type stars with a novel and powerful compressible high-order un-structured spectral-difference (chorus) code (j. comput. physics vol. 290, 190-211, 2015). recent observations have revealed th... | convection in oblate late-type stars |
our goal is to address the mystery of the origin of magnetic fields in white dwarf stars. one telling clue in this mystery is that spectroscopic mass determinations for magnetic white dwarf stars are consistently higher (averaging ~0.93msun) than for non-magnetic white dwarf stars (approximately 0.6msun). through our w... | are all magnetic white dwarf stars massive? |
one of the major constraints of simulating magnetic flux emergence and the development of solar eruptive activities is the need to cover large spatial scales but still resolve the necessary physics at different phases of the evolution. this has lead to developments in simulating the independent parts of the emergence-e... | developments in model-coupling for simulations of flux emergence and coronal dynamics |
helioseismology has revealed that the solar differential rotation profile exhibits an outward decrease in angular velocity at all latitudes across the upper 5% of the sun by radius. this near-surface shear layer (nssl) is thought to play a significant role in defining the nature of large-scale convective patterns that ... | sustaining a solar-like near-surface shear layer and its applicability to other stars |
we selected all of the known transiting planets from the nasa exoplanet archive (http://exoplanetarchive.ipac.caltech.edu/) for which the planet mass exceeds 0.1 mjup, the orbital period is shorter than 3.5 days, and the star has an effective temperature below 6100 k. the effective temperature cut-off ensures that only... | vizier online data catalog: dissipation in exoplanet hosts from tidal spin-up (penev+, 2018) |
the efficiency of tidal dissipation in convective zones of stars and giant planets depends, in part, on the response of a three-dimensional fluid flow to the periodic deformation due to the equilibrium tide — a problem considered by jean-paul zahn in his phd thesis. we review recent results on this problem and present ... | on the frequency-dependent effective viscosity of laminar and turbulent flows |
for nonrotating stars, previous studies have shown that the leading-order dynamics within stellar convection zones becomes insensitive to diffusive processes once the rayleigh number, ra, exceeds a threshold value. thus, the spatially integrated convective kinetic energy asymptotes to a value that is nearly independent... | the scaling law for rotating stellar convection in the high-rayleigh-number regime |
the habitability of distant exoplanets is dependent upon many factors one of which is the activity of their host stars. to learn about which stars are most likely to flare, a recent study examines tens of thousands of stellar flares observed by kepler.need for a broader sampleartists rendering of a flaring dwarf star. ... | which of kepler's stars flare? |
this paper compares the tycho and geneva stellar evolution codes. standard stellar evolution models do not match observations without adjustment of free parameters, yet predictive models are essential. we examine the level at which tycho’s addition of hydrodynamic mixing effects the evolution of massive stars by compar... | a comparison of mixing in stellar evolution codes tycho and geneva |
with the successes of the space missions corot, kepler, and k2 and of the large ground-based surveys, we are living a revolution for our knowledge of planetary systems. as of today, more than 2950 confirmed exoplanets have been discovered. they orbit a broad diversity of host stars with different masses and evolutionar... | tidal dissipation in the host star of short-period exoplanetary systems |
it is debated wether close-in giants planets can form in-situ and if not, which mechanisms are responsible for their migration. one of the observable tests for migration theories is the current value of the obliquity. but after the main migration mechanism has ended, the combined effects of tidal dissipation and the ma... | a double zone dynamical model for the tidal evolution of the obliquity |
the nature of a star's magnetic field is determined primarily by the stellar mass and rotation rate. using spectropolarimetric techniques, we have now mapped the surface magnetic fields of some 100 stars across a wide range of these fundamental parameters. some of the biggest surprises have been in the nature of the ma... | exoplanet environments and radio signatures |
intermediate-mass (2-8 m⊙) main-sequence stars with a to mid-b spectral types occupy an x-ray "desert" of weak intrinsic emission between low- and high-mass stars. lacking the wind-shock driven emission of massive, o and early b stars or the convectively-driven magnetic reconnection flaring activity of later-type stars... | x-ray emission properties of intermediate-mass, pre-main-sequence stars |
as established by ground based surveys, white dwarfs with hydrogen atmospheres pulsate as they cool across the temperature range, 12500k< teff < 10800k . known as davs or zz ceti stars, their oscillations are attributed to overstable g-modes excited by convective driving. the effective temperature at the blue edg... | davs: red edge and outbursts |
recent progress in stellar observations opens new perspectives in understanding stellar evolution and structure. however, complex interactions in the turbulent radiating plasma together with effects of magnetic fields and rotation make inferences of stellar properties uncertain. the standard 1d mixing-length-based evol... | 3d realistic radiative hydrodynamic modeling of a moderate-mass star: effects of rotation |
the depth of the convection zone in models of white dwarf stars is a sensitive function of effective temperature. in a pulsating white dwarf, this sensitivity can lead to a modulation of the underlying sinusoidal pulsations, producing non-sinusoidal light curves. working backwards, we can use these light curves to cons... | testing white dwarf convection theory with darc and the whole earth telescope |
the interplay between stellar rotation and turbulent flows is a major ingredient for vertical angular momentum transport in stellar convection zone. combined with the centrifugal force and the buoyancy force due to pole-equator temperature gradients one can expect a large-scale flow structure that is usually referred t... | driving magnetic activity: differential rotation, flow structures, and surface patterns |
m-dwarf stars are smaller and less luminous than our sun. in their interiors, convection dominates energy transport from the center of the star to their surface. this ball-like geometry is unique among all the stars on the main-sequence; in our sun, solar convection is bounded from below by regions of stable stratifica... | dynamics in the ball: models for fully convective, rotating m-dwarf stars |
we compare and contrast the nature of silanols on open, two-dimensional surfaces comprising amorphous and crystalline siliceous materials. we compare the thermal treatment of silanols in both sets of materials, using several forms of spectroscopy for characterization. the ramifications of the observed differences on ap... | characterization of silanol defect sites on amorphous versus crystalline 2-d silicate surfaces |
this work discusses theoretical limits of chromospheric heating by shock waves in stars with low surface gravity. the computations are self consistent, and based on waves generated in stellar convection zones. we employ the new finding of the mixing length parameter α = 1.8. the ca~ii~h+k and mg~ii~h+k fluxes are compu... | limits of shock heating for the chromospheres of low-gravity stars |
the potential habitability of exoplanets is traditionally assessed by determining whether or not its orbit falls within the circumstellar `habitable zone' of its star [1]. however, this metric does not readily account readily for changes in the abundance of greenhouse gases and their associated radiative forcing as a r... | long term planetary habitability and the carbonate-silicate cycle: the effect of planet size |
to interpret the high-quality data produced from recent space-missions it is necessary to study convection under realistic stellar conditions. we describe the multi-dimensional, time implicit, fully compressible, hydrodynamic, implicit large eddy simulation code music, currently being developed at the university of exe... | convective penetration in stars |
plato (planetary transits and oscillations of stars) has been selected for esa's m3 launch opportunity end 2025. plato will carry out high-precision, long-term photometric and asteroseismic monitoring of a large number of stars. it will provide a large sample of small planets around bright stars, including terrestrial ... | the plato mission |
the laps (live atmospheres-of-planets simulator) is a live 1d version of the lmd global climate model that provides an accelerated and interactive simulation of the climate of terrestrial planets and exoplanets.this tool was designed for students to explore the «classical habitable zone», defined as the range of orbita... | the laps project : a live 1d radiative-convective model to explore the possible climates of terrestrial planets and exoplanets. |
the most energetic part of the sun, its interior, due to its plasma parameters is hidden below the solar surface and invisible to the observer. nevertheless, the solar interior generates the energy and provokes atmospheric magnetic activity. despite great progress in both observational and simulational methods, the mec... | the role of partial ionization in solar chromospheric heating |
we present a state of the art of precise spectral opacity calculations illustrated by stellar applications. the essential role of laboratory experiments to check the quality of the computed data is underlined. we review some x-ray and xuv laser and z-pinch photo-absorption measurements as well as x-ray emission spectro... | detailed opacity calculations for stellar models |
the tachocline</u> region inside the sun, where the rigidly rotating radiative core meets the differentially rotating convection zone, is thought to be crucial for generating the sun's magnetic field. low-mass fully convective stars do not possess a tachocline</u> and were originally expected to generate on... | a self-consistent dynamo model for fully convective stars |
clouds play an important role in the radiative transfer of planetary atmospheres: they are key elements of the climate system and influence the planet's spectral appearance. given the thousands of exoplanets discovered so far, including some dozens of earth-sized exoplanets, the feasibility of remote sensing of exoplan... | thermal infrared emission spectra of terrestrial exoplanets influenced by multi-layer clouds |
simulations of the rise of buoyant magnetic flux ropes through the solar convection zone show that flux ropes break up and cease to be buoyant if their magnetic twist is too weak. similarly, simulations of the emergence of magnetic flux ropes through the photosphere into the solar atmosphere show that buoyant flux rope... | investigations of the role of magnetic twist in flux rope emergence |
planetary atmospheres are dynamic entities. their story begins with the inventory of volatiles delivered in the course of planet formation. over the subsequent history of the planet, the atmosphere evolves through outgassing of volatiles from the interior of the planet, through chemical reactions between the atmosphere... | planetary atmospheres: where do they come from? where do they go? |
this paper provides a brief overview of the formation of stellar fossil magnetic fields and what potential instabilities may occur given certain configurations of the magnetic field. one such instability is the purely magnetic tayler instability, which can occur for poloidal, toroidal, and mixed poloidal-toroidal axisy... | on the stability of a general magnetic field topology in stellar radiative zones |
the habitable zone (hz) is commonly defined as the range of distances from a host star within which liquid water, a key requirement for life, may exist at a planet's surface. substantially more co2 than present in earth's modern atmosphere is required to maintain clement temperatures for most of the hz, with several ba... | a limited habitable zone for complex life |
we present a series of numerical simulations that model the convection zones in giant planets and stars. each simulation consists of a rotating spherical shell that is highly stratified by gravity. with this suite of numerical experiments we explore the convective structures that are achieved as the convective rossby n... | morphological regimes of rotating convection in stratified spherical shells |
the comparison between large-eddy simulations (les) and experimental data is problematic due to the inherent filtering of the les data. filtering techniques (leonard 1974, germano 1992, klein 2018) can be applied, allowing for a better comparison between these data sets. the experimental data from the turbulent mixing ... | using lab-scale mixing experiments to inform les of stellar convection |
to interpret high-quality data produced from recent space missions such as kepler and tess, it is necessary to develop theoretical and computational modeling of convection under realistic stellar conditions. a major open question surrounding convection in stars is the amount of convective overshooting that takes place ... | a comparison of the filling factor in hydrodynamic simulations of pre-main-sequence stars |
hot jupiters are one of the few types of planets that can currently be observationally characterized. under strong external radiation forcing, hot jupiters show a variety of atmosphere circulation pattern. due to spectrum exhibits information and our knowledge in atmosphere dynamic of the hot jupiter, some researchers ... | a model for hot jupiter with bottom thermal perturbation |
the canonical undestanding of stellar convection has recently been put under doubt due to helioseismic results and global 3d convection simulations. this "convective conundrum" is manifested by much higher velocity amplitudes in simulations at large scales in comparison to helioseismic results, and the difficulty in re... | effects of rotation and surface forcing on deep stellar convection zones |
current state-of-the-art computational modeling makes it possible to build realistic models of stellar convection zones and atmospheres that take into account chemical composition, radiative effects, ionization, and turbulence. the standard 1d mixing-length-based evolutionary models are not able to capture many physica... | 3d modeling of the structure and dynamics of a main-sequence f-type star |
m dwarfs are the most common and longest-lived stars in the galaxy, and they host some of the most exciting planetary systems discovered so far. the transiting exoplanet survey satellite (tess) and the james webb space telescope (jwst) are targeting m dwarfs in particular, to search for rocky planets in habitable zones... | the stellar rotation and gyrochronology of cool stars |
we present a theoretical model of the near-surface shear layer (nssl) of the sun. convection cells deeper down are affected by the sun's rotation, but this is not the case in a layer just below the solar surface due to the smallness of the convection cells there. based on this idea, we show that the thermal wind balanc... | the near-surface shear layer (nssl) of the sun: a theoretical model |
in this paper, we investigate the upward overshooting by three-dimensional numerical simulations. we find that the above convectively stable zone can be partitioned into three layers: the thermal adjustment layer (mixing both entropy and material), the turbulent dissipation layer (mixing material but not entropy), and ... | upward overshooting in turbulent compressible convection. i.effects of the relative stability parameter, the prandtl number, and the péclet number |
(abstract only) we present a short review of flare stars. flare stars, or uv ceti stars, are a type of eruptive variable star, defined by their flaring behavior-a rapid (minutes) increase in brightness, followed by a slower (hours) decrease. this short review outlines current knowledge about flare stars, their importan... | flare stars: a short review (abstract) |
we present multidimensional modeling of convection and oscillations in main-sequence stars somewhat more massive than the sun, using three separate approaches: 1) using the 3-d planar stellarbox radiation hydrodynamics code to model the envelope convection zone and part of the radiative zone. our goals are to examine t... | 2-d and 3-d models of convective turbulence and oscillations in intermediate-mass main-sequence stars |
the 3d thermal convection in the boussinesq approximation with heating from below and dynamo in the cube are considered. we study dependence of the convection intensity and magnetic field generation on the latitude in $\beta$-plane approximation. it is shown that kinetic energy gradually increases from the poles to the... | latitude dependence of convection and magnetic field generation in the cube |
motivated by understanding the dynamics of stellar and planetary interiors, we have performed a set of direct numerical simulations of boussinesq convection in a rotating full sphere. the domain is internally heated with fixed temperature and stress-free boundary conditions, but fixed heat flux and no-slip boundary con... | large-scale vortices and zonal flows in spherical rotating convection - corrigendum |
this thesis details a line of work, carried out over several years, that has seen the development of a next generation, self-consistently evolved, rotating stellar evolution model grid. the forthcoming chapters describe their application in studying various observed phenomena. stellar rotation is the third fundamental ... | next generation stellar models with rotation |
the habitability of a planet can be severely affected by the activity of its host star. several young solar type and fully convective stars observed by the kepler and k2 missions produce superflares that are up to a thousand times more energetic than those of the sun. these superflares can increase the level of uv irra... | surface and oceanic habitability of terrestrial planets under impacts of flares |
while most debris disks consist of dust with little or no gas, a fraction have significant amounts of gas detected via emission lines of co, ionized carbon, and/or atomic oxygen. almost all such gaseous debris disks known are around a-type stars with ages up to 50 myr. we show, using semianalytic disk evolution modelin... | a primordial origin for the gas-rich debris disks around intermediate-mass stars |
gas giant planets are differentially rotating magnetic objects that have strong and complex interactions with their environment. in our solar system, they interact with their numerous moons while exoplanets with very short orbital periods (hot jupiters), interact with their host star. the dissipation of waves excited b... | hydrodynamical modelling of tidal dissipation in gas giant planets at the time of space missions |
a proposed setting for thermonuclear (type ia) supernovae is a white dwarf that has gained mass from a companion to the point of carbon ignition in the core. there is a simmering phase in the early stages of burning that involves the formation and growth of a core convection zone. one aspect of this phase is the convec... | sensitivity of 3d convective urca simulations to changes in urca reactions |
most prior works studying tidal interactions in tight star/planet or star/star binary systems have employed linear theory of a viscous fluid in a uniformly-rotating two-dimensional spherical shell. however, compact systems may have sufficiently large tidal amplitudes for nonlinear effects to be important. we compute ti... | do nonlinear effects disrupt tidal dissipation predictions in convective envelopes? |
understanding the internal rotation of low mass stars all along their evolution is of primary interest when studying their rotational dynamics, internal mixing and magnetic field generation. in this context, helio- and asteroseismology probe angular velocity gradients deep within solar type stars at different evolution... | 2d dynamics of the radiative core of low mass stars |
in this work, we present a study of the propagation of low-frequency magneto-acoustic waves into the solar chromosphere within small-scale inclined magnetic fields over a quiet-magnetic network region utilizing near-simultaneous photospheric and chromospheric dopplergrams obtained from the hmi instrument onboard sdo sp... | a study of the propagation of magnetoacoustic waves in small-scale magnetic fields using solar photospheric and chromospheric dopplergrams: hmi/sdo and mast observations |
we present evidence of hitherto undiscovered global-scale oscillations in the near-surface shear layer of the sun. these oscillations are seen as large-scale variations of radial shear in both the zonal and meridional flows relative to their mean values. the variations cover all or most of a visible hemisphere, and rev... | evidence of a quasiperiodic global-scale oscillation in the near-surface shear layer of the sun |
stars expand by up to a couple orders of magnitude during the post-main-sequence. in many planetary systems, this expansion will lead to the engulfment of nearby planets and/or brown dwarfs (hereafter substellar bodies, sbs). the engulfment of an sb could explain observations of evolved stars with unusually high surfac... | the hydrodynamics of planetary engulfment |
1) introductionif an earth-like planet with a large amount of water is drifted towards its host star, the surface temperature increases, which leads the atmosphere to enter a catastrophic runaway greenhouse state [1-4]. studying this runaway greenhouse effect allows to better determine the runaway greenhouse insolation... | how background gases can delay the onset of the runaway greenhouse? insights from 1d and 3d modeling. |
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