Dynamics of active region flux tubes in the solar convection zone

Y. Fan*
National Center for Atmospheric Research, 3080 Center Green Drive, Boulder, CO 80301, USA

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I review recent results on modeling the buoyant rise of active region scale flux tubes in the solar convective envelope based on both a thin flux tube model incorporating the effects of giant-cell convection as well as direct 3D spherical-shell anelastic MHD simulations. It is found that the dynamic evolution of the flux tube changes from magnetic buoyancy dominated to convection dominated as the initial field strength of the flux tube varies from about 100 kG to 15 kG. Mid-range field strengths of about 40 - 50 kG seem to produce emerging loops that best match the observed properties of solar active regions.

The initial twist of the tube cannot be too high in order for the tilt of the emerging loops to be dominated by the effect of the Coriolis force and be consistent with the mean tilt of solar active regions. Future high resolution (low diffusivity) global-scale MHD simulations in a rotating, fully convecting spherical shell representative of the solar convective envelope are needed to self-consistently study the formation and dynamic rise of active region scale flux tubes in the solar convection zone.

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Keywords : MHD – Sun: dynamo – Sun: interior