Laboratory experiments on the transition to MHD dynamos

Abstract

We present observations of a mechanically forced liquid-metal dynamo experiment and review international efforts in this field. As the magnetic Reynolds number is increased, our measurements show lengthening of the decay time of pulsed magnetic fields. These measurements quantify the approach to magnetic field self-generation. While an external field is applied, large fluctuations occur in the magnetic response of the system. We analyse these fluctuations to characterize the liquid-metal velocity field. This analysis suggests that turbulence strongly influences the approach to self-generation in a forced liquid-metal flow.