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Constraining the physical and chemical evolution of molecular clouds is essential to our understanding of star formation. These investigations often necessitate knowledge of some local representative number density of the gas along the line…

Astrophysics of Galaxies · Physics 2025-04-02 Brandt A. L. Gaches , Michael Y. Grudić

Turbulent convection is certainly one of the most important and thorny issues in stellar physics. Our deficient knowledge of this crucial physical process introduces a fairly large uncertainty concerning the internal structure and evolution…

Solar and Stellar Astrophysics · Physics 2018-04-25 M. Gabriel , K. Belkacem

The effects of rapid rotation on stellar evolution can be profound. We are now beginning to gather enough data to allow a realistic comparison between different physical models. Two key tests for any theory of stellar rotation are first…

Solar and Stellar Astrophysics · Physics 2015-05-30 Adrian T. Potter , Christopher A. Tout , John J. Eldridge

The conceptual landscape of convection has two simple gateways: optimal function and random form. Optimal convection adjusts toward a univariate ideal called neutrality. Convection form involves elements (parcels, bubbles, drafts) whose…

Adaptation and Self-Organizing Systems · Physics 2025-04-02 Brian E. Mapes

Vertical thermal convection is a non-equilibrium system in which both buoyancy and shear forces play a role in driving the convective flow. Beyond the onset of convection, the driven dissipative system exhibits chaotic dynamics and…

Fluid Dynamics · Physics 2024-11-27 Zheng Zheng , Laurette S. Tuckerman , Tobias M. Schneider

Theoretical descriptions of convective overshooting often rely on a one-dimensional parameterization of the flow called the filling factor for convection. Several definitions of the filling factor have been developed, based on: (1) the…

Solar and Stellar Astrophysics · Physics 2024-12-04 M. -G. Dethero , J. Pratt , D. G. Vlaykov , I. Baraffe , T. Guillet , T. Goffrey , A. Le Saux , A. Morison

The time-dependent Ginzburg-Landau equation and the Swift-Hohenberg equation, both added with a stochastic term, are proposed to describe cloud pattern formation and cloud regime phase transitions of shallow convective clouds organized in…

Pattern Formation and Solitons · Physics 2021-03-24 Diana L. Monroy , Gerardo G. Naumis

We present the first hydrodynamic, multi-dimensional simulations of He-shell flash convection. Specifically, we investigate the properties of shell convection at a time immediately before the He- luminosity peak during the 15th thermal…

Astrophysics · Physics 2009-11-11 Falk Herwig , Bernd Freytag , Robert M. Hueckstaedt , Francis X. Timmes

Convection-diffusion equations provide the basis for describing heat and mass transfer phenomena as well as processes of continuum mechanics. To handle flows in porous media, the fundamental issue is to model correctly the convective…

Numerical Analysis · Computer Science 2012-08-29 A. Churbanov , P. Vabishchevich

We assess the ability to image the photosphere of red supergiants and, in particular Betelgeuse, through the modelling of the observed linear polarization in atomic spectral lines. We also aim to analyse the resulting images over time, to…

Solar and Stellar Astrophysics · Physics 2018-12-19 A. López Ariste , P. Mathias , B. Tessore , A. Lèbre , M. Aurière , P. Petit , N. Ikhenache , E. Josselin , J. Morin , M. Montargès

In this lecture I present the way stars can be modeled in two dimensions and especially the fluid flows that are driven by rotation. I discuss some of the various ways of taking into account turbulence and conclude this contribution by a…

Solar and Stellar Astrophysics · Physics 2015-06-15 Michel Rieutord

Regions of stellar and planetary interiors that are unstable according to the Schwarzschild criterion, but stable according to the Ledoux criterion, are subject to a form of oscillatory double-diffusive (ODD) convection often called…

Solar and Stellar Astrophysics · Physics 2015-01-22 Toby S. Wood , Pascale Garaud , Stephan Stellmach

Multi-fluid models have recently been proposed as an approach to improving the representation of convection in weather and climate models. This is an attractive framework as it is fundamentally dynamical, removing some of the assumptions of…

Fluid Dynamics · Physics 2021-06-18 Daniel Shipley , Hilary Weller , Peter Clark , Will McIntyre

The cores of main sequence intermediate- and high-mass stars are convective. Mixing at the radiative-convective boundary, waves excited by the convection, and magnetic fields generated by convective dynamos all influence the main sequence…

Solar and Stellar Astrophysics · Physics 2023-08-02 Daniel Lecoanet , Philipp V. F. Edelmann

Rayleigh-B\'enard convection, i.e. the flow of a fluid between two parallel plates that is driven by a temperature gradient, is an idealised setup to study thermal convection. Of special interest are the statistics of the turbulent…

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…

Solar and Stellar Astrophysics · Physics 2016-05-17 Joyce A. Guzik , T. H. Morgan , N. J. Nelson , C. Lovekin , K. Kosak , I. N. Kitiashvili , N. N. Mansour , A. Kosovichev

Evolved cool stars of various masses are major cosmic engines, delivering substantial mechanical and radiative feedback to the interstellar medium through strong stellar winds and supernova ejecta. These stars play a pivotal role in…

Solar and Stellar Astrophysics · Physics 2024-02-02 Andrea Chiavassa , Kateryna Kravchenko , Jared A. Goldberg

Recently Pasetto et al. have proposed a new method to derive a convection theory appropriate for the implementation in stellar evolution codes. Their approach is based on the simple physical picture of spherical bubbles moving within a…

Solar and Stellar Astrophysics · Physics 2016-03-09 Marcelo M. Miller Bertolami , Maxime Viallet , Vincent Prat , Wasilij Barsukow , Achim Weiss

The circumgalactic medium (CGM) plays a pivotal role in regulating gas flows around galaxies and thus shapes their evolution. However, the details of how galaxies and their CGM co-evolve remain poorly understood. We present a new…

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…

Solar and Stellar Astrophysics · Physics 2021-07-28 Irina N. Kitiashvili , Alan A. Wray