Bifurcations in Spherical MHD Models

A series of numerical studies on the behaviour of magnetic fields and motions in a spherical body of an electrically conducting incompressible fluid have been carried out. The magnetic field was assumed to be maintained by a given electromotive force inside the body and to continue as a potential fi...

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Bibliographic Details
Published in:Studia geophysica et geodaetica 1998-01, Vol.42 (3), p.320-327
Main Authors: Fuchs, H, K-H, Rädler
Format: Article
Language:English
Subjects:
Bifurcations
Boundary conditions
Configurations
Differential rotation
Electric potential
Electromotive forces
Fluid flow
Free surfaces
Hartmann number
Incompressible flow
Incompressible fluids
Magnetic field
Magnetic fields
Potential fields
Rotation
Studies
Surface stability
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Summary:A series of numerical studies on the behaviour of magnetic fields and motions in a spherical body of an electrically conducting incompressible fluid have been carried out. The magnetic field was assumed to be maintained by a given electromotive force inside the body and to continue as a potential field in outer space. In view of the motion an external forcing was taken into account, and boundary conditions were considered which correspond to a stress-free surface. The stability of several steady states has been studied as well as the evolutions starting from unstable states. In this paper a configuration with a poloidal magnetic field and a differential rotation, both symmetric about the same axis, is considered. This configuration is stable only for sufficiently small Hartmann numbers but evolves, if disturbed, in the case of larger Hartmann numbers toward a non-axisymmetric state. In this case the well-known symmetrization effect of differential rotation in magnetic fields is destroyed.
ISSN:0039-3169
1573-1626
DOI:10.1023/A:1023356720631