AAS 205th Meeting, 9-13 January 2005
Session 34 Stellar Structure and Evolution
Oral, Monday, January 10, 2005, 10:00-11:30am, Royal Palm 4-6

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[34.03] Core Convection and Dynamo Action in Rotating A-type Stars

M.K. Browning (JILA, University of Colorado), A.S. Brun (DSM/DAPNIA/SAp, CEA-Saclay, France, and JILA), J. Toomre (JILA, University of Colorado)

We have carried out 3-D simulations of core convection and dynamo activity within A-type stars of two solar masses at a range of rotation rates. Our models consider the inner 30% by radius of such stars, thus capturing the entire convective core and a portion of the surrounding radiative envelope within the spherical computational domain. Using the anelastic spherical harmonic (ASH) code on massively parallel supercomputers, we solve the compressible MHD equations to examine highly nonlinear and evolving flows and magnetic fields. Vigorous dynamo action is realized, with initial seed magnetic fields amplified by many orders of magnitude and sustained against ohmic decay. The resulting complex magnetism possesses energy densities comparable to that in the flows, is structured on many scales, and serves to modify the convective and zonal flows that gave rise to it. The differential rotation established in progenitor hydrodynamic simulations is weakened, and waxes and wanes in strength as the simulations evolve. We discuss the morphology and evolution of the flows and magnetic fields, the penetrative properties of the convection, and the nature of the dynamo process.

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© 2004. The American Astronomical Society.