Turbulent dynamos driven by convection

The generation of magnetic fields by the turbulent motions of a conducting fluid driven by thermal convection in the incompressible case is studied by direct numerical simulations at Rayleigh numbers up to 200 times critical and Prandtl numbers 0.2 and 1. Our results are consistent with a dynamo effect which occurs for magnetic Reynolds numbers above a few tens, in the presence of, as well as in the absence of, rotation around the vertical axis. In all cases, the magnetic field is more intermittent than the velocity field.