An investigation into high conductivity dynamo action driven by rotating convection

As a step towards constructing a physically realistic model of a fast dynamo, we study numerically the kinematic evolution of a magnetic field in a convectively driven flow in a rapidly rotating cylindrical annulus. Convection maintains the quasi-geostrophic balance whilst developing more complicated time-dependence as the Rayleigh number is increased. We incorporate the effects of Ekman suction and investigate the nature of any dynamo action resulting from two chaotic flows obtained in this manner. In order to investigate the fast dynamo limit we introduce the idea of an effective growth rate and examine how this varies as a function of magnetic Prandtl number Pm (proportional to the magnetic Reynolds number). Even for the largest value of Pm considered, a clearly identifiable asymptotic behaviour is not established. Nevertheless, the available evidence is suggestive of a fast dynamo process.