Global Simulations of Stellar Dynamos
Abstract
In the Sun and other stars of its type, the tachocline of shear at the base of the convective envelope is generally believed to play a crucial role in facilitating the generation of large-scale magnetic fields. I will describe a series of three-dimensional MHD simulations of dynamo action by convection that can penetrate into a stably stratified tachocline, and contrast these with other models which include only the convective layer itself. Our simulations, conducted using the Anelastic Spherical Harmonic (ASH) code, allow us to assess the roles played by differential rotation, convection, magnetic pumping, and large-scale circulations in building organized magnetism. The inclusion of a simplified tachocline leads to the generation of magnetic fields with several properties that are strikingly reminiscent of the observed solar fields. We find that strong toroidal fields of roughly 3000 G strength can be generated at the base of the convection zone, and that these fields often exhibit antisymmetric parity akin to that observed in sunspots. We will also show, however, that organized fields can also be realized in some cases where no tachocline is present: in the interiors of fully convective low-mass stars, and in more rapidly rotating solar analogues. We will discuss the roles that rotation and stratification play in promoting the generation of such organized fields.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMSH11B..08B
- Keywords:
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- 7524 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Magnetic fields;
- 7544 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY / Stellar interiors and dynamo theory