Jean-François Pinton, Laboratoire de Physique, Ecole Normale Supérieure de Lyon and CNRS
Several experiments have aimed at producing dynamo action in the laboratory. Landmarks are the solid rotor experiment of Lowes and Wilkinson (1963), the fluid dynamos in the Riga and Karlsruhe experiments (2000). I will discuss issues related to dynamo generation from turbulent or organized flows, and describe the results recently obtained in the VKS (von Kármán Sodium) experiment. A highly turbulent flow of sodium is set into motion inside a cylinder by the counter-rotation of propellers. A statistically steady, self-sustained dynamo is generated when the propellers are in exact counter-rotation above a critical rate. When one propeller rotates faster than the other, global rotation is imparted to the fluid, as in astrophysical objects. The magnetic field exhibits a variety of dynamical regimes, some of which very similar to the reversal of the Earth magnetic field.