Solar Convective Dynamo Action With A Tachocline

Type Conference Paper
Names Nicholas Featherstone, A. S. Brun, M. S. Miesch, B. P. Brown, J. Toomre
Proceedings Title Bulletin of the American Astronomical Society
Conference Name American Astronomical Society, AAS Meeting #215, #322.02
Volume 42
Pages 323
Date January 1, 2010
Library Catalog NASA ADS
Abstract We present continuing simulations of solar-like convection penetrating into the tachocline at the base of the convection zone and examine the resulting dynamo action. Prior simulations using the 3-D anelastic spherical harmonic (ASH) code of convection in a full spherical shell admitting penetration into a tachocline have yielded differential rotation profiles whose latitudinal contrast is considerably smaller than in simulations without penetration. We believe that the relatively soft stabilizing entropy gradients in the overshooting regions may have resulted in unusually strong circulations that worked against the Reynolds stresses, thus diminishing the differential rotation. Here we turn to ASH simulations with more realistic stiffer entropy gradients and reduced diffusivities in the radiative zone. We report on the hydrodynamic balances achieved within the region of penetration that allows the convection zone to return to differential rotation profiles in closer accord with helioseismic deductions, including possessing a tachocline of shear. We then examine the possibilities for dynamo action in this system and find that weak wreathes of toroidal field, similar to those found in simulations of faster rotating suns, are realized in the convection zone. Convective pumping of these fields into the tachocline leads to the generation of strong axisymmetric toroidal fields there, with oppositely signed polarities about the equator. We examine the temporal variation of these magnetic fields as well as their effects on the angular momentum transport within the bulk of the convection zone.
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