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We study the underlying physics of cosmic-ray (CR) driven instabilities that play a crucial role for CR transport across a wide range of scales, from interstellar to galaxy cluster environments. By examining the linear dispersion relation…

Astrophysics of Galaxies · Physics 2023-12-18 Mohamad Shalaby , Timon Thomas , Christoph Pfrommer , Rouven Lemmerz , Virginia Bresci

Shear flow instabilities can profoundly affect the diffusion of momentum in jets, stars, and disks. The Richardson criterion gives a sufficient condition for instability of a shear flow in a stratified medium. The velocity gradient $V'$ can…

Solar and Stellar Astrophysics · Physics 2015-05-18 Daniel Lecoanet , Ellen G. Zweibel , Richard H. D. Townsend , Yi-Min Huang

Mergers of binary neutron stars likely lead to the formation of a hypermassive neutron star (HMNS), which is metastable and eventually collapses to a black hole. This merger scenario is thought to explain the phenomenology of short…

General Relativity and Quantum Cosmology · Physics 2014-01-22 Daniel M. Siegel , Riccardo Ciolfi

Simulations of the magnetorotational instability (MRI) in a homogeneous shearing box have shown that the asymptotic strength of the magnetic field declines steeply with increasing resolution. Here I model the MRI driven dynamo as a large…

High Energy Astrophysical Phenomena · Physics 2011-02-11 Ethan T. Vishniac

We conduct a linear analysis of axisymmetric magnetorotational instability (MRI) in a magnetized cylindrical Taylor-Couette (TC) flow for its standard version (SMRI) with a purely axial background magnetic field and two further types --…

Fluid Dynamics · Physics 2022-06-07 A. Mishra , G. Mamatsashvili , F. Stefani

We investigate the action of the magnetorotational instability (MRI) in the context of iron-core collapse. Exponential growth of the field on the rotation time scale by the MRI will dominate the linear growth process of field line…

Astrophysics · Physics 2009-11-07 Shizuka Akiyama , J. Craig Wheeler , David L. Meier , Itamar Lichtenstadt

We propose that the strength of angular momentum transport in accretion discs threaded by net vertical magnetic field is determined by a self-regulation mechanism: the magnetorotational instability (MRI) grows until its own turbulent…

High Energy Astrophysical Phenomena · Physics 2023-04-18 Mitchell C. Begelman , Philip J. Armitage

The magnetorotational instability (MRI) is the most promising mechanism by which angular momentum is efficiently transported outwards in astrophysical discs. However, its application to protoplanetary discs remains problematic. These discs…

Earth and Planetary Astrophysics · Physics 2015-06-16 Matthew W. Kunz , Geoffroy Lesur

We investigate analytically the magnetic instability in a rotating and electrically conducting fluid induced by an imposed magnetic field with its associated electric current. The short-wavelength approximation is used in the linear…

Earth and Planetary Astrophysics · Physics 2013-08-22 Xing Wei

Sweet-Parker current sheets in high Lundquist number plasmas are unstable to tearing, suggesting they will not form in physical systems. Understanding magnetic reconnection thus requires study of the stability of a current sheet as it…

Plasma Physics · Physics 2018-03-02 Elizabeth A. Tolman , Nuno F. Loureiro , Dmitri A. Uzdensky

Magnetic buoyancy (MBI) and Parker instabilities are strong, generic instabilities expected to occur in most astrophysical systems with sufficiently strong magnetic fields. In galactic and accretion discs, large-scale magnetic fields are…

Astrophysics of Galaxies · Physics 2025-04-11 Yasin Qazi , Anvar. Shukurov , Frederick. A. Gent , Devika. Tharakkal , Abhijit. B. Bendre

The magnetorotational instability (MRI) is thought to play a key role in the formation of stars and black holes by sustaining the turbulence in hydrodynamically stable Keplerian accretion discs. In previous experiments the MRI was observed…

We show by means of a perturbative weakly nonlinear analysis that the axisymmetric magnetorotational instability (MRI) of a viscous, resistive, incompressible rotating shear flow in a thin channel gives rise to a real Ginzburg-Landau…

Astrophysics · Physics 2008-11-26 O. M. Umurhan , K. Menou , O. Regev

We numerically evolve turbulence driven by the magnetorotational instability (MRI) in a 3D, unstratified shearing box and study its structure using two-point correlation functions. We confirm Fromang and Papaloizou's result that shearing…

Astrophysics of Galaxies · Physics 2011-02-11 Xiaoyue Guan , Charles F. Gammie , Jacob B. Simon , Bryan M. Johnson

We examine some debated points in current discussions about rotating stars: the shape, the gravity darkening, the critical velocities, the mass loss rates, the hydrodynamical instabilities, the internal mixing and N--enrichments. The study…

Solar and Stellar Astrophysics · Physics 2015-06-22 Andre Maeder , Georges Meynet

Magnetohydrodynamic (MHD) turbulence is of key importance in many high-energy astrophysical systems, where MHD instabilities can amplify local magnetic field over very short time scales. Specifically, the magnetorotational instability (MRI)…

High Energy Astrophysical Phenomena · Physics 2018-03-30 Philipp Mösta , Christian D. Ott , David Radice , Luke F. Roberts , Erik Schnetter , Roland Haas

In preparation for an experimental study of magnetorotational instability (MRI) in liquid metal, we present non-ideal two-dimensional magnetohydrodynamic simulations of the nonlinear evolution of MRI in the experimental geometry. The…

Astrophysics · Physics 2009-11-13 Wei Liu , Jeremy Goodman , Hantao Ji

Magnetic fields represent a crucial aspect of the physics and astrophysics of neutron stars. Despite its great relevance, the internal magnetic field configuration of neutron stars is very poorly constrained by the observations, and…

High Energy Astrophysical Phenomena · Physics 2015-06-18 Riccardo Ciolfi

The effect of the Hall term on the evolution of the magnetorotational instability (MRI) in weakly ionized accretion disks is investigated using local axisymmetric simulations. First, we show that the Hall term has important effects on the…

Astrophysics · Physics 2009-11-07 Takayoshi Sano , James M. Stone

We examine the small-scale dynamics of black hole accretion disks in which radiation pressure exceeds gas pressure. Local patches of disk are modeled by numerically integrating the equations of radiation MHD in the flux-limited diffusion…

Astrophysics · Physics 2008-11-26 N. J. Turner , J. M. Stone , J. H. Krolik , T. Sano