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Dynamo action in the presence of an imposed magnetic field
Author(s) -
Featherstone N.A.,
Browning M.K.,
Brun A.S.,
Toomre J.
Publication year - 2007
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.200710888
Subject(s) - dynamo , physics , magnetic field , solar dynamo , dynamo theory , mercury's magnetic field , astrophysics , convection , stars , radiative transfer , magnetohydrodynamics , l shell , quantum electrodynamics , mechanics , earth's magnetic field , quantum mechanics
Abstract Dynamo action within the cores of Ap stars may offer intriguing possibilities for understanding the persistent magnetic fields observed on the surfaces of these stars. Deep within the cores of Ap stars, the coupling of convection with rotation likely yields magnetic dynamo action, generating strong magnetic fields. However, the surface fields of the magnetic Ap stars are generally thought to be of primordial origin. Recent numerical models suggest that a primordial field in the radiative envelope may possess a highly twisted toroidal shape. We have used detailed 3‐D simulations to study the interaction of such a twisted magnetic field in the radiative envelope with the core‐dynamo operating in the interior of a 2 solar mass A‐type star. The resulting dynamo action is much more vigorous than in the absence of such a fossil field, yielding magnetic field strengths (of order 100 kG) much higher than their equipartition values relative to the convective velocities. We examine the generation of these fields, as well as the growth of large‐scale magnetic structure that results from imposing a fossil magnetic field. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)