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Astron. Astrophys. 349, 189-202 (1999)

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Differential rotation and magnetic fields in stellar interiors

H.C. Spruit

Max-Planck-Institut für Astrophysik, Postfach 1523, D-85740 Garching bei München, Germany (henk@mpa-garching.mpg.de)

Received 15 January 1999 / Accepted 30 May 1999


The processes contributing to the evolution of an initially weak magnetic field in a differentially rotating star are reviewed. These include rotational smoothing (akin to convective expulsion) and a list of about 5 instabilities, among them magnetorotational instability, buoyancy instability, and pinch-type instabilities. The important effects of thermal and magnetic diffusion on these instabilities are analyzed in some detail. The first instability to set in is a pinch-type instability. It becomes important in modifying the field configuration before magnetic buoyancy-driven instabilities set in. The evolution of an initially strong field remains a more open question, including the old problem whether dynamically stable magnetic equilibria exist in stars.

Key words: instabilities – Magnetohydrodynamics (MHD) – stars: magnetic fields – stars: rotation – Sun: rotation

© European Southern Observatory (ESO) 1999

Online publication: August 25, 1999