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A linear but global numerical model for the magnetorotational instability (MRI) in disk geometry is considered to estimate the instability parameters for galaxies. Similarity rules suggested by a local analysis are applied to reveal a…

Astrophysics · Physics 2016-08-16 L. L. Kitchatinov , G. Rüdiger

We show, by means of a perturbative weakly nonlinear analysis, that the axisymmetric magneto-rotational instability (MRI) in a magnetic Taylor-Couette (mTC) flow in a thin-gap gives rise, for very small magnetic Prandtl numbers (P_m), to a…

Astrophysics · Physics 2015-05-13 O. Regev

The interaction of differential rotation and toroidal fields that are current-free in the gap between two corotating axially unbounded cylinders is considered. It is shown that nonaxisymmetric perturbations are unstable if the rotation rate…

Solar and Stellar Astrophysics · Physics 2015-06-15 G. Ruediger , M. Gellert , M. Schultz , R. Hollerbach , F. Stefani

We perform 3D vertically-stratified local shearing-box ideal MHD simulations of the magnetorotational instability (MRI) that include a net vertical magnetic flux, which is characterized by beta_0 (ratio of gas pressure to magnetic pressure…

High Energy Astrophysical Phenomena · Physics 2015-06-11 Xue-Ning Bai , James M. Stone

We present direct numerical simulations of dynamo action in a forced Roberts flow. The behavior of the dynamo is followed as the mechanical Reynolds number is increased, starting from the laminar case until a turbulent regime is reached.…

Fluid Dynamics · Physics 2015-06-26 P. D. Mininni , D. C. Montgomery

The magnetorotational instability (MRI) triggers turbulence and enables outward transport of angular momentum in hydrodynamically stable accretion discs. By using the WKB approximation and methods of singular function theory, we resolve two…

Solar and Stellar Astrophysics · Physics 2015-03-19 Oleg N. Kirillov , Frank Stefani

This paper is a detailed report on a programme of simulations used to settle a long-standing issue in the dynamo theory and demonstrate that the fluctuation dynamo exists in the limit of large magnetic Reynolds number Rm>>1 and small…

The linear stability of electrically driven flow of liquid metal in circular channel in the presence of vertical magnetic field is studied. It is shown that the instability threshold of such flow is determined by magnetorotational…

Astrophysics · Physics 2007-11-20 I. V. Khalzov , A. I. Smolyakov , V. I. Ilgisonis

We demonstrate that the critical magnetic Reynolds number $Rm_c$ for a turbulent non-helical dynamo in the low magnetic Prandtl number $Pm$ limit (i.e. $Pm = Rm/Re \ll 1$) can be significantly reduced if the flow is submitted to global…

Fluid Dynamics · Physics 2017-06-28 Kannabiran Seshasayanan , Vassilios Dallas , Alexandros Alexakis

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

Though usually treated in isolation, the magnetorotational and gravitational instabilities (MRI and GI) may coincide at certain radii and evolutionary stages of protoplanetary discs and active galactic nuclei. Their mutual interactions…

High Energy Astrophysical Phenomena · Physics 2017-12-27 A. Riols , H. Latter

We carry out a comprehensive analysis of the behavior of the magnetorotational instability (MRI) in viscous, resistive plasmas. We find exact, non-linear solutions of the non-ideal magnetohydrodynamic (MHD) equations describing the local…

Astrophysics · Physics 2009-11-13 Martin E. Pessah , Chi-kwan Chan

Magnetorotational instability (MRI) is one of the most important and most common instabilities in astrophysics, it is widely accepted that it serves as a source of turbulent viscosity in accretion disks -- the most energy efficient objects…

Astrophysics · Physics 2007-05-23 J. Szklarski

We perform a local stability analysis of rotational flows in the presence of a constant vertical magnetic field and an azimuthal magnetic field with a general radial dependence. Employing the short-wavelength approximation we develop a…

Fluid Dynamics · Physics 2014-11-14 Oleg N. Kirillov , Frank Stefani , Yasuhide Fukumoto

(Abriged) The magnetorotational instability (MRI) is believed to be an efficient way to transport angular momentum in accretion discs. It has also been suggested as a way to amplify magnetic fields in discs, the instability acting as a…

Astrophysics · Physics 2009-11-13 G. Lesur , G. I. Ogilvie

The magnetorotational instability (MRI) is the leading candidate for driving turbulence, angular momentum transport, and accretion in astrophysical disks. I consider the linear theory of the MRI in a thin, equatorial disk in the Kerr…

Astrophysics · Physics 2009-11-10 Charles F. Gammie

We study the influence of the choice of transport coefficients (viscosity and resistivity) on MHD turbulence driven by the magnetorotational instability (MRI) in accretion disks. We follow the methodology described in paper I: we adopt an…

Astrophysics · Physics 2009-11-13 S. Fromang , J. Papaloizou , G. Lesur , T. Heinemann

Using direct simulations of hydromagnetic turbulence driven by random polarized waves it is shown that dynamo action is possible over a wide range of magnetic Prandtl numbers from 10^-3 to 1. Triply periodic boundary conditions are being…

Astrophysics · Physics 2010-01-15 Axel Brandenburg

The magnetorotational instability (MRI) can destabilize hydrodynamically stable rotational flows, thereby allowing angular momentum transport in accretion disks. A notorious problem for MRI is its questionable applicability in regions with…

Solar and Stellar Astrophysics · Physics 2013-08-09 Oleg N. Kirillov , Frank Stefani

The stability problem of MHD Taylor-Couette flows with toroidal magnetic fields is considered in dependence on the magnetic Prandtl number. Only the most uniform (but not current-free) field with B\_in = B\_out has been considered. For high…

Astrophysics · Physics 2008-09-22 M. Gellert , G. Ruediger