Towards a rapidly rotating liquid sodium dynamo experiment

P. Cardin - D. Brito - D. Jault - H.-C. Nataf - J.-P. Masson

Laboratoire de Géophysique Interne et Tectonophysique, Observatoire de Grenoble, Université Joseph Fourier B.P. 53, 38041 Grenoble, France

Abstract
The main characteristics of the Earth's dynamo are reviewed. The combined actions of Coriolis and Lorentz forces lead to the so-called ``magnetostrophic'' regime. We derive an estimate of the power needed to sustain the magnetic field in this regime. We show that an experiment with liquid sodium can be designed to operate in the magnetostrophic regime. Such an experiment would bring most valuable information on the mechanisms of planetary dynamos. In order to prepare this large-scale experiment and explore the magnetostrophic balance, a smaller scale liquid sodium set-up has been designed and is being built. It consists of a rapidly rotating spherical shell filled with liquid sodium, in which motions are set by spinning at a different rotation rate an inner core permeated by a strong magnetic field. We discuss the processes that can be explored with this new device. Figs 3, Refs 28.