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A&A 440, 1041-1049 (2005)
DOI: 10.1051/0004-6361:20053261
Stellar evolution with rotation and magnetic fields
III. The interplay of circulation and dynamo
A. Maeder and G. MeynetGeneva Observatory, 1290 Sauverny, Switzerland
e-mail: [andre.maeder;georges.meynet]@obs.unige.ch
(Received 19 April 2005 / Accepted 20 May 2005)
Abstract
We examine the effects of the magnetic field created by the Tayler-Spruit dynamo
in differentially rotating stars. Magnetic fields of the order of a few 104 G are present
through most of the stellar envelope, with the exception of the outer layers.
The diffusion coefficient for the transport of angular momentum is
very large and it imposes nearly solid body rotation during the MS phase. In turn, solid body rotation
drives meridional circulation currents which are much faster than usual and leads to much larger
diffusion coefficients than the magnetic diffusivity for the chemical species.
The consequence is that the interplay of the thermal and magnetic instabilities
favours the chemical transport of elements, while there would be no transport in models with magnetic field only. We also discuss the effects on the stellar interior, lifetimes and HR diagram.
Key words: stars: rotation -- stars: magnetic fields -- stars: evolution
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