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The question is addressed whether stellar differentially rotating radiative zones (like the solar tachocline) excite nonaxisymmetric r-modes which can be observed. To this end the hydrodynamical stability of latitudinal differential…

Solar and Stellar Astrophysics · Physics 2015-05-13 L. L. Kitchatinov , G. Rüdiger

We simulate the ionization environment of z ~ 20 luminous objects formed within the framework of the current CDM cosmology and compute their UV escape fraction. These objects are likely single very massive stars that are copious UV…

Astrophysics · Physics 2009-11-10 Daniel Whalen , Tom Abel , Michael L. Norman

Rotational mixing, the key process in stellar evolution, transports angular momentum and chemical elements in stellar radiative zones. In the past two decades, an emphasis has been placed on the turbulent transport induced by the vertical…

Solar and Stellar Astrophysics · Physics 2020-03-25 Junho Park , Vincent Prat , Stéphane Mathis

We present the first realistic 3D simulations of flame front instabilities during type I X-ray bursts. The unperturbed front is characterised by the balance between the pressure gradient and the Coriolis force of a spinning neutron star…

High Energy Astrophysical Phenomena · Physics 2019-09-25 Yuri Cavecchi , Anatoly Spitkovsky

We derive the equations for the propagation of relativistic ionization fronts in both static and moving gases. We focus on the supersonic R-type phase that occurs right after a source turns on, and we compare the nonrelativistic and…

Astrophysics · Physics 2008-11-26 Paul R. Shapiro , Ilian T. Iliev , Marcelo A. Alvarez , Evan Scannapieco

We consider the scenario of a magnetic field orthogonal to a front separating two media of different temperatures and densities, such as cold and warm interstellar gas, in a 2-D plane-parallel geometry. A linear stability analysis is…

Astrophysics of Galaxies · Physics 2011-02-11 Jennifer M. Stone , Ellen G. Zweibel

The nonlinear evolution of unstable C-type shocks in weakly ionized plasmas is studied by means of time-dependent magnetohydrodynamical simulations. This study is limited to shocks in magnetically dominated plasmas (in which the Alfven…

Astrophysics · Physics 2009-10-30 James M. Stone

A long-standing question is whether radiative cooling can lead to local condensations of cold gas in the hot atmospheres of galaxies and galaxy clusters. We address this problem by studying the nature of local instabilities in rotating,…

Astrophysics of Galaxies · Physics 2015-06-19 Carlo Nipoti , Lorenzo Posti

We present initial attempts to include the multi-dimensional nature of radiation transport in hydrodynamical simulations of the small-scale structure that arises from the line-driven instability in hot-star winds. Compared to previous 1D or…

Astrophysics · Physics 2009-11-10 Luc Dessart , S. P. Owocki

The linear stability of stratified two-phase flows in rectangular ducts is studied numerically. The linear stability analysis takes into account all possible infinitesimal three-dimensional disturbances and is carried out by solution of the…

Fluid Dynamics · Physics 2020-04-09 Alexander Gelfgat , Neima Brauner

The radial profiles of gas, stars, and far ultraviolet radiation in 20 dwarf Irregular galaxies are converted to stability parameters and scale heights for a test of the importance of two-dimensional (2D) instabilities in promoting star…

Astrophysics of Galaxies · Physics 2015-06-03 Bruce G. Elmegreen , Deidre A. Hunter

We present three-dimensional simulations of the dynamical bar-mode instability in magnetized and differentially rotating stars in full general relativity. Our focus is on the effects that magnetic fields have on the dynamics and the onset…

General Relativity and Quantum Cosmology · Physics 2015-06-16 Luca Franci , Roberto De Pietri , Kyriaki Dionysopoulou , Luciano Rezzolla

The relationship between a decaying strong turbulence and kinetic instabilities in a slowly expanding plasma is investigated using two-dimensional (2-D) hybrid expanding box simulations. We impose an initial ambient magnetic field…

Linear theory is a well developed framework for characterizing instabilities in weakly collisional plasmas, such as the solar wind. In the previous instalment of this series, we analyzed ~1.5M proton and alpha particle Velocity Distribution…

Solar and Stellar Astrophysics · Physics 2023-07-26 Mihailo M. Martinovic , Kristopher G. Klein

All gasdynamical models for the evolution of gaseous content of galaxies assume that cooling from the hot, virialized phase to the cold phase occured through some sort of thermal instability. Subsequent formation of colder clouds embedded…

Astrophysics · Physics 2007-05-23 Milan M. Cirkovic

In Part I of this paper we described an equilibrium model of a jet in the gravitational field corresponding to the rigid-rotation region of the galactic disk. We used linear stability analysis to find the waveguide-resonance instability of…

Astrophysics · Physics 2009-11-13 V. L. Afanasiev , S. N. Dodonov , S. S. Khrapov , A. V. Moiseev , V. V. Mustsevoy

In-situ observations of the solar wind (SW) plasma from 0.29 to 1AU show that the protons and alpha particles are often non-Maxwellian, with evidence of kinetic instabilities, temperature anisotropies, differential ion streaming, and…

Space Physics · Physics 2019-05-15 Leon Ofman

In collision-poor plasmas from space, three distinct ion-ion instabilities can be driven by the proton beams streaming along the background magnetic field: left-hand resonant, non-resonant, and right-hand resonant instabilities. These…

Solar and Stellar Astrophysics · Physics 2020-08-19 S. M. Shaaban , M. Lazar , R. A. López , S. Poedts

We discuss the theory of coupled ionization--dissociation fronts produced when molecular clouds are exposed to $\lambda < 1110$\AA\ radiation from hot stars. A steady, composite structure is developed, which generally includes an ionized…

Astrophysics · Physics 2009-10-28 Frank Bertoldi , B. T. Draine

Motivated by the problem of the formation of active regions from a deep-seated solar magnetic field, we consider the nonlinear three-dimensional evolution of magnetic buoyancy instabilities resulting from a smoothly stratified horizontal…

Astrophysics · Physics 2009-11-13 Evy Kersale , David W. Hughes , Steven M. Tobias