AAS 204th Meeting, June 2004
Session 7 A Walk Through the HR Diagram
Poster, Monday, May 31, 2004, 9:20am-6:30pm, Ballroom

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[7.07] Simulations of Core Convection and Dynamo Activity in A-type Stars at a Range of Rotation Rates

M.K. Browning (JILA, University of Colorado-Boulder), A.S. Brun (CEA Saclay; JILA), J. Toomre (JILA, University of Colorado-Boulder)

We present the results of nonlinear 3--D simulations of magnetic dynamo action by core convection within A-type stars of 2 solar masses, at 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. We solve the compressible Navier-Stokes equations in the anelastic approximation 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 and the magnitude of the differential rotation sustained as the rotation rate in our simulations is varied.

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Bulletin of the American Astronomical Society, 36 #2
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