EDP Sciences
Free access
Volume 414, Number 3, February II 2004
Page(s) 1065 - 1070
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20034178

A&A 414, 1065-1070 (2004)
DOI: 10.1051/0004-6361:20034178

Ambient magnetic fields and dynamos: Pre-main sequence stars and elsewhere

D. Moss

Department of Mathematics, University of Manchester, Manchester M13 9PL, UK
(Received 11 August 2003 / Accepted 21 October 2003)

The effects of an ambient (i.e. "external") poloidal magnetic field on mean field dynamo action in a sphere are investigated. It is found that an ambient field of strength comparable to that of the poloidal field of the isolated dynamo will inhibit dynamo action. This ambient field will normally be considerably weaker than the typical total field resulting from  $\alpha^2\omega$ dynamo action. Given earlier similar results for disc dynamos, this appears to be a general result. Applications to pre-main sequence stars and the history of magnetic white dwarfs are discussed.

Key words: magnetic fields -- stars: evolution -- stars: chemically peculiar -- stars: magnetic fields -- stars: pre-main sequence

© ESO 2004