HR: 1340h
AN: GP43A-0891    [Abstracts]
TI: Scaling properties of planetary dynamos
AU: * Aubert, J
EM: aubert@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75252 France
AU: Christensen, U
EM: christensen@linmpi.mpg.de
AF: Max-Planck-Institute for Solar System Research, Max-Planck-Strasse 2, Katlenburg-Lindau, DEU 37191
AB: We have performed a parameter space survey for numerical MHD dynamos in rotating spherical shells, varying all relevant control parameters.Simple scaling laws have been derived for the typical amplitude of the convection flow, of the zonal flow and of the magnetic field. The key parameter in these scaling relationships is the buoyancy flux, which measures the quantity of energy made available to the dynamo, irrespectively of the nature (chemical or thermal) of convection. The scaling for the magnetic field is strikingly independant on rotation rate of the planet. This fact is discussed in connection with the role of the Coriolis force in the dynamo system and dimensional analysis. The scalings are then applied to evaluate the buoyancy flux in the Earth's core. The result is compatible with an aged (more than three billion years old) inner core. On Jupiter the surface magnetic field, surface zonal flow and excess heat flow are also found to be compatible with the scalings. Further modelling is presented to treat the more complex cases of Uranus and Neptune.
DE: 1510 Dynamo: theories and simulations
DE: 5400 PLANETARY SCIENCES: SOLID SURFACE PLANETS
DE: 5700 PLANETARY SCIENCES: FLUID PLANETS
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005