Transition from laminar to turbulent dynamo: the effect of varying Prandtl number

Abstract

We carry out numerical dynamo simulations in a spherical shell to assess the influence of varying Prandtl number on the morphology of the induced magnetic field in both cases when the convection is laminar and turbulent. We work in a regime of large magnetic Prandtl number ( ) due to computational constraints of the full three-dimensional numerical model. We consider dynamos driven by thermal convection in the regimes of small and unit Prandtl numbers. Unlike the laminar convection, in the turbulent regime the morphology of the induced magnetic fields depends only weakly on the Prandtl number. For both values of considered the magnetic field is non-dipolar and small-scale. Together with the previous results of other authors, who found that the morphology of the magnetic field does not change substantially with when is small, the results of our study suggest that the induced magnetic field does not vary substantially with regardless of the strength of the magnetic diffusion.