Magnetohydrodynamics of stellar interiors

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AWARD NO: AST-0607495PI: Pascale GaraudINSTITUTION: University of California Santa CruzTITLE: Magnetohydrodynamics of stellar interiorsABSTRACTThis research is part of a long-term project to better understand the magnetohydrodynamicsof stellar interiors. Towards this end, a 2-dimensional dynamical structureand evolution code is being constructed which incorporates the interaction between largescalemagnetic fields and flows. The effects of small scale fields and flows are alsomodeled through turbulence closure. Here the PI will continue developing the corenumerical algorithm (which is already producing results concerning the dynamics of thesolar radiative region) and testing the closure model (which has been successfully testedagainst experimental data for rotating shear flows). Specific tasks to be undertakeninclude: 1) Developing computational methods to extrapolate numerical results to solarvalues of the various diffusion parameters and testing them against solar observations. 2)Further improving and extending the existing closure model to take into account turbulentenergy transport and testing the model predictions against 3D numerical simulations ofrotating convection. And 3) combining the radiative zone model with the turbulenceclosure model to obtain a complete numerical algorithm designed to study the magnetohydrodynamicsof the interior of a solar type star, and obtaining qualitative results for avariety of stellar parameters (structure, internal field strength, rotation rate). Futureplanned work will then investigate in turn: the stability of the models obtained to variouskinds of axially symmetric and non-axially symmetric instabilities; the dynamicalbehavior of the model with respect to the generation of a magnetic cycle; and the carefulquantitative comparison with existing data from various sources (e.g. asteroseismology,Doppler Imaging, Mount Wilson Ca-line survey).The modeling approach being developed will include geometric aspects of the dynamics(missing from 1D models) without the heavy computational load of 3D models. Thus thework here will be of value to many other areas of astronomy - particularlyasteroseismology and studies of the solar interior where the sophistication of theobservations now demand better models. Therefore, once fully developed, these tools willbe made available to the astronomical community. This work also supports a graduatestudent who will be trained in numerical magnetohydrodynamic modeling andinterpreting/comparing these results with observations.