HR: 0800h
AN: DI31A-0255    [Abstracts]
TI: Dynamo Bifurcation in Geodynamo Models
AU: Morin, V
EM: vmorin@ucsd.edu
AF: University of California San Diego, Department of Mechanical and Aerospace Engineering, Jacobs School of engineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0411, United States
AU: * Dormy, E
EM: dormy@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, Equipe MAG, Ecole Normale Supérieure, Département de Physique, LRA, 24 rue Lhomond, Paris, 75005, France
AB: We investigate the dynamo bifurcation --i.e. the onset of dynamo action-- in numerical models relevant to the Earth's core. As usual in such models, controlling parameters are very remote from relevant geophysical values, sometimes by factors in excess of a million. We show how the nature of the dynamo bifurcation happens to be very sensitive to the parameters regime. We report supercritical bifurcations, subcritical bifurcations and isola. We describe how this behavior depends on the relevant parameters. Finally, we show that two distinct dynamo branches with different energies can be described for a given set of parameters. While viscous effects are not negligeable in simulations, this could be related to the weak and strong field branches which have been proposed in the context of the Geodynamo.
DE: 1507 Core processes (1213, 8115)
DE: 1510 Dynamo: theories and simulations
DE: 4410 Bifurcations and attractors
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting