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Alfv\'enic turbulence in space is usually imbalanced: amplitudes of waves propagating parallel and anti-parallel to the mean magnetic field $B_0$ are unequal. It is commonly accepted that the turbulence is driven by (counter-)collisions…

Space Physics · Physics 2016-11-29 Yuriy Voitenko , Johan De Keyser

Ion-neutral collisions may lead to the damping of Alfven waves in chromospheric and prominence plasmas. Neutral helium atoms enhance the damping in certain temperature interval, where the ratio of neutral helium and neutral hydrogen atoms…

Solar and Stellar Astrophysics · Physics 2015-06-12 T. V. Zaqarashvili , M. L. Khodachenko , R. Soler

We consider the problem of incompressible, forced, nonhelical, homogeneous, isotropic MHD turbulence with no mean magnetic field. This problem is essentially different from the case with externally imposed uniform mean field. There is no…

Astrophysics · Physics 2008-11-26 A. A. Schekochihin , S. C. Cowley , S. F. Taylor , J. L. Maron , J. C. McWilliams

We study the formation of giant dense cloud complexes and of stars within them by means of SPH numerical simulations of the mildly supersonic collision of gas streams (``inflows'') in the warm neutral medium (WNM). The resulting…

We present high resolution numerical simulations of compressible magnetohydrodynamic (MHD) turbulence. We concentrate on studies of spectra and anisotropy of velocity and density. We describe a technique of separating different…

Astrophysics · Physics 2016-08-30 Jungyeon Cho , A. Lazarian

Molecular clouds are supersonically turbulent. This turbulence governs the initial mass function and the star formation rate. In order to understand the details of star formation, it is therefore essential to understand the properties of…

Astrophysics of Galaxies · Physics 2015-06-17 Adam Ginsburg , Christoph Federrath , Jeremy Darling

In this paper we explore the relationship between protostellar outflows and turbulence in molecular clouds. Using 3-D numerical simulations we focus on the hydrodynamics of multiple outflows interacting within a parsec scale volume. We…

I describe the scenario of molecular cloud (MC) evolution that has emerged over the past decade or so. MCs can start out as cold atomic clouds formed by compressive motions in the warm neutral medium (WNM) of galaxies. Such motions can be…

Astrophysics of Galaxies · Physics 2010-09-22 Enrique Vazquez-Semadeni

Hydrodynamic supersonic turbulence can only prevent local gravitational collapse if the turbulence is driven on scales smaller than the local Jeans lengths in the densest regions, a very severe requirement (Paper I). Magnetic fields have…

Astrophysics · Physics 2010-10-28 F. Heitsch , M. -M. Mac Low , R. S. Klessen

Recent observations of column densities in molecular clouds find lognormal distributions with power-law high-density tails. These results are often interpreted as indications that supersonic turbulence dominates the dynamics of the observed…

Astrophysics of Galaxies · Physics 2015-05-19 K. Tassis , D. A. Christie , A. Urban , J. L. Pineda , T. Ch. Mouschovias , H. W. Yorke , H. Martel

This investigation deals with the analysis of stagnation point heat transfer and corresponding flow features of hydromagnetic viscous incompressible fluid over a vertical shrinking sheet. The considered sheet is assumed to be permeable and…

Fluid Dynamics · Physics 2015-11-20 Rakesh Kumar , Shilpa Sood

Galactic and intergalactic flows often exhibit relative motion between the cold dense gas and the hot diffuse medium. Such multiphase flows -- involving gas at different temperatures, densities, and ionization states -- for instance,…

Astrophysics of Galaxies · Physics 2025-10-07 Ritali Ghosh , Max Gronke , Prateek Sharma , Alankar Dutta

We derive the nonlinear fractional surface wave equation that governs compression waves at an interface that is coupled to a viscous bulk medium. The fractional character of the differential equation comes from the fact that the effective…

Fluid Dynamics · Physics 2017-11-29 Julian Kappler , Shamit Shrivastava , Matthias F. Schneider , Roland R. Netz

We study collisions between two strongly interacting atomic Fermi gas clouds. We observe exotic nonlinear hydrodynamic behavior, distinguished by the formation of a very sharp and stable density peak as the clouds collide and subsequent…

Quantum Gases · Physics 2012-01-18 James Joseph , John E. Thomas , Manas Kulkarni , Alexander G. Abanov

We present 2D adiabatic magnetohydrodynamic (MHD) simulations of a shock interacting with groups of two or three cylindrical clouds. We study how the presence of a nearby cloud influences the dynamics of this interaction, and explore the…

Astrophysics of Galaxies · Physics 2015-06-22 R. Alūzas , J. M. Pittard , S. A. E. G. Falle , T. W. Hartquist

Intermittency is an essential property of astrophysical fluids, which demonstrate an extended inertial range. As intermittency violates self-similarity of motions, it gets impossible to naively extrapolate the properties of fluid obtained…

Astrophysics · Physics 2011-05-10 A. Lazarian

This paper is devoted to the study of the gravitational instability of a medium permeated by a uniform magnetic field along which a circularly polarized Alfven wave propagates. We concentrate on the case of perturbations purely transverse…

Astrophysics · Physics 2009-11-07 Adriana Gazol , Thierry Passot

We present the first magnetohydrodynamic model of the stellar chromospheric heating and acceleration of the outer atmospheres of cool evolved stars, using alpha Tau as a case study. We used a 1.5D MHD code with a generalized Ohm's law that…

Solar and Stellar Astrophysics · Physics 2014-09-15 V. S. Airapetian , J. E. Leake , K. G. Carpenter

This paper investigates the nature of the MHD turbulence excited by the streaming of accelerated cosmic rays in a shock wave precursor. The two recognised regimes (non-resonant and resonant) of the streaming instability are taken into…

Astrophysics · Physics 2009-11-11 Guy Pelletier , Martin Lemoine , Alexandre Marcowith

We performed one-dimensional hydrodynamic simulations with detailed cooling, heating and chemical processes to examine the thermal stability of shocked gas in cold neutral medium (CNM) and molecular clouds. We find that both CNM and…

Solar and Stellar Astrophysics · Physics 2015-06-16 Takuhiro Aota , Tsuyoshi Inoue , Yuri Aikawa