FLUX TUBES AND SCALING IN MHD DYNAMO SIMULATIONS

MHD simulations of compressible convection in a layer heated from below are discussed and the results analysed in various ways. The ultimate aim of these simulations is to understand the generation and evolution of the magnetic field in the sun. The formation of flux tubes is addressed, and it is concluded that random field line stretching plays the dominant role, which is in contrast to vortex tubes where both shear instabilities and vortex stretching contribute almost equally to the generation of vorticity. Magnetic flux tubes occur preferentially near stagnation points, but there remains a significant flow component along the tube. Various scaling properties of the magnetic field generated in such simulations are investigated. Multifractal dimensions, cancellation exponents, and generalized power spectra are computed. While the spectra show a tendency for power law scaling, no such behavior is found for the cancellation exponent. Finally, implications for the generation of large-scale fields in the solar dynamo are discussed.