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Global MHD phenomena and their importance for stellar surfaces

Published online by Cambridge University Press:  26 August 2011

Rainer Arlt*
Affiliation:
Astrophysikalisches Institut Potsdam, An der Sternwarte 16 D-14482 Potsdam, Germany email: rarlt@aip.de
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Abstract

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This review is an attempt to elucidate MHD phenomena relevant for stellar magnetic fields. The full MHD treatment of a star is a problem which is numerically too demanding. Mean-field dynamo models use an approximation of the dynamo action from the small-scale motions and deliver global magnetic modes which can be cyclic, stationary, axisymmetric, and non-axisymmetric. Due to the lack of a momentum equation, MHD instabilities are not visible in this picture. However, magnetic instabilities must set in as a result of growing magnetic fields and/or buoyancy. Instabilities deliver new timescales, saturation limits and topologies to the system probably providing a key to the complex activity features observed on stars.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2011

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