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Simulations of core convection and resulting dynamo action in rotating A-type stars

Published online by Cambridge University Press:  02 March 2005

Matthew K. Browning
Affiliation:
JILA, University of Colorado at Boulder, 440 UCB, Boulder CO, USA 80309-0440 email: matthew.browning@colorado.edu
Allan S. Brun
Affiliation:
JILA, University of Colorado at Boulder, 440 UCB, Boulder CO, USA 80309-0440 email: matthew.browning@colorado.edu SAp, CEA-Saclay, 91191 Gif-sur-Yvette, France
Juri Toomre
Affiliation:
JILA, University of Colorado at Boulder, 440 UCB, Boulder CO, USA 80309-0440 email: matthew.browning@colorado.edu
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Abstract

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We present the results of 3–D nonlinear simulations of magnetic dynamo action by core convection within A-type stars of 2 $M_{\odot}$ with a range of rotation rates. We consider the inner 30% by radius of such stars, with the spherical domain thereby encompassing the convective core and a portion of the surrounding radiative envelope. The compressible Navier-Stokes equations, subject to the anelastic approximation, are solved to examine highly nonlinear flows that span multiple scale heights, exhibit intricate time dependence, and admit magnetic dynamo action. Small initial seed magnetic fields are found to be amplified greatly by the convective and zonal flows. The central columns of strikingly slow rotation found in some of our progenitor hydrodynamic simulations continue to be realized in some simulations to a lesser degree, with such differential rotation arising from the redistribution of angular momentum by the nonlinear convection and magnetic fields. We assess the properties of the magnetic fields thus generated, the extent of the convective penetration, the magnitude of the differential rotation, and the excitation of gravity waves within the radiative envelope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Type
Contributed Papers
Copyright
© 2004 International Astronomical Union