Journal Article

Viscosity alpha in rotating spherical shear flows with an external magnetic field

A. Drecker, R. Hollerbach and G. Rüdiger

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 298, issue 4, pages 1030-1034
Published in print August 1998 | ISSN: 0035-8711
Published online August 1998 | e-ISSN: 1365-2966 | DOI:
Viscosity alpha in rotating spherical shear flows with an external magnetic field

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We study the turbulent behaviour induced by the magnetic shear instability for a magnetized, incompressible fluid in a spherical shell. A differential rotation that is decreasing outwards but hydrodynamically stable according to the Rayleigh criterion is prescribed, and an external, uniform magnetic field is imposed parallel to the rotation axis. Our main concern in this paper is the fully global treatment of this magnetohydrodynamical system, so we focus particular attention on the influence of the boundary conditions. Non-linear, steady solutions are presented for stress-free as well as for rigid boundary conditions for one specific model with a fixed strength of the external magnetic field and a fixed differential rotation rate. We calculate the eddy viscosity νT and the viscosity alpha αSS resulting from the total stress tensor. These turbulence parameters turn out to differ drastically depending on the boundary conditions for the flow. An investigation of the radial structure of the viscosity alpha (whilst varying the differential rotation law) shows that the enhanced generation of turbulence takes place mainly in the boundary layers of the shell.

Keywords: instabilities; MHD; turbulence

Journal Article.  0 words. 

Subjects: Astronomy and Astrophysics

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