Mechanisms of planetary and stellar dynamos

Emmanuel Dormy Ludovic Petitdemange, Martin Schrinner

CNRS, Equipe MAG (ENS-IPGP),
LRA, Département de Physique,
Ecole Normale Supérieure,
24 rue Lhomond, 75005 Paris, France

Solar and Astrophysical Dynamos and Magnetic Activity
Proceedings IAU Symposium No. 294, 163-173, 2012
A.G. Kosovichev, E.M. de Gouveia Dal Pino, & Y. Yan, eds.
Location: Beijin, China.

Abstract. We review some of the recent progress on modeling planetary and stellar dynamos. Particular attention is given to the dynamo mechanisms and the resulting properties of the field. We present direct numerical simulations using a simple Boussinesq model. These simulations are interpreted using the classical mean-field formalism. We investigate the transition from steady dipolar to multipolar dynamo waves solutions varying different control parameters, and discuss the relevance to stellar magnetic fields. We show that owing to the role of the strong zonal flow, this transition is hysteretic. In the presence of stress-free boundary conditions, the bistability extends over a wide range of parameters.