Buoyancylimited thin shell dynamos
Abstract
Axisymmetric nonlinear meanfield dynamos in spherical shells are investigated that attempt to model the gross effects of a dynamo operating in a thin layer at the base of a convective envelope. A form of magnetic buoyancy restricts the fields to finite amplitude. As the shell thickness decreases, the excitation conditions and spatial structure of even and odd parity modes become almost identical. For very thin shells the field forms a number of almost disjoint cells. Mixed parity solutions are found which typically evolve very slowly toward pure odd or even parity solutions. The time scale of these slow variations is of the order of a hundred global diffusion times.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 December 1990
 Bibcode:
 1990A&A...240..142M
 Keywords:

 Dynamo Theory;
 Magnetohydrodynamics;
 Solar Cycles;
 Spherical Shells;
 Buoyancy;
 Convection Currents;
 Solar Physics