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M. Rempel, M.P. Rast (HAO/NCAR)
The structure of the overshoot region at the base of solar convection zone is crucial to the storage of strong toroidal magnetic field produced there by the solar dynamo. Both the mean thermodynamic stratification and the statistical properties of the convective fluctuations affect the storage capabilities of the region. Overshoot models of the past, based on the non local mixing-length theory, generally produce a shallow weakly subadiabatic region with a steep transition to the radiative interior. A more recent estimation by Xiong & Deng (Mon. Not. R. Astron. Soc. 327, 1137) suggests a larger subadiabaticity and a smoother transition to the radiative gradient. Numerical studies have to date contributed little to constraining these simpler models, largely because they are unable to match the very low values of radiative conductivity found in the solar interior. The abnormally high values of conductivity generally employed lead to much more vigorous convection and much deeper convective penetration than anticipated. To address this deficiency directly we adopt a formulation which explicitly separates of the thermal conductivity into a turbulent and a radiative component, and employ a novel thermal relaxation scheme which accelerates the approach to equilibrium in the deep radiative layers even at very low values of the latter. This separation also enables adjustment of the convective properties apart from the radiative ones in the lower half of the convection zone. Preliminary results suggest that the structure of the overshoot region is highly sensitive to the properties of the convection in the lower half of the convection zone.
NCAR is sponsored by the National Since Foundation.
The author(s) of this abstract have provided an email address for comments about the abstract: rempel@hao.ucar.edu
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.