Magnetohydrodynamics of stellar interiors

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

AWARD NO: AST-0607495 PI: Pascale Garaud INSTITUTION: University of California Santa Cruz TITLE: Magnetohydrodynamics of stellar interiors ABSTRACT This research is part of a long-term project to better understand the magnetohydrodynamics of stellar interiors. Towards this end, a 2-dimensional dynamical structure and evolution code is being constructed which incorporates the interaction between largescale magnetic fields and flows. The effects of small scale fields and flows are also modeled through turbulence closure. Here the PI will continue developing the core numerical algorithm (which is already producing results concerning the dynamics of the solar radiative region) and testing the closure model (which has been successfully tested against experimental data for rotating shear flows). Specific tasks to be undertaken include: 1) Developing computational methods to extrapolate numerical results to solar values of the various diffusion parameters and testing them against solar observations. 2) Further improving and extending the existing closure model to take into account turbulent energy transport and testing the model predictions against 3D numerical simulations of rotating convection. And 3) combining the radiative zone model with the turbulence closure model to obtain a complete numerical algorithm designed to study the magnetohydrodynamics of the interior of a solar type star, and obtaining qualitative results for a variety of stellar parameters (structure, internal field strength, rotation rate). Future planned work will then investigate in turn: the stability of the models obtained to various kinds of axially symmetric and non-axially symmetric instabilities; the dynamical behavior of the model with respect to the generation of a magnetic cycle; and the careful quantitative 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 the work here will be of value to many other areas of astronomy - particularly asteroseismology and studies of the solar interior where the sophistication of the observations now demand better models. Therefore, once fully developed, these tools will be made available to the astronomical community. This work also supports a graduate student who will be trained in numerical magnetohydrodynamic modeling and interpreting/comparing these results with observations.