MAGNETIC-STRUCTURES IN A DYNAMO SIMULATION

We use three-dimensional simulations to study compressible convection in a rotating frame with magnetic fields and overshoot into surroundin g stable layers. The, initially weak, magnetic field is amplified and maintained by dynamo action and becomes organized into flux tubes that are wrapped around vortex tubes. We also observe vortex buoyancy whic h causes upward flows in the cores of extended downdraughts. An analys is of the angles between various vector fields shows that there is a t endency for the magnetic field to be parallel or antiparallel to the v orticity vector, especially when the magnetic field is strong. The mag netic energy spectrum has a short inertial range with a slope compatib le with k(+1/3) during the early growth phase of the dynamo. During th e saturated state the slope is compatible with k(-1). A simple analysi s based on various characteristic timescales and energy transfer rates highlights important qualitative ideas regarding the energy budget of hydromagnetic dynamos.