FLUX EXPULSION BY INHOMOGENEOUS TURBULENCE

Flux expulsion is an important consequence of the interaction of magne tic fields with fluid convection and has been well studied for particu lar cases of steady, single-cell flows. Here we examine a related phen omenon in inhomogeneous turbulence using direct numerical simulations. To understand our numerical results, we analyse average properties of our model, and obtain mean transport coefficients which can be used t o describe the approach of the system to its final state. For the kine matic problem these transport coefficients give an excellent predictio n of the expulsion process; however, the enhanced transport is suppres sed by dynamical back-reaction of the Lorentz force. Finally, we discu ss the astrophysical implications for magnetic fields in stellar conve ction zones. Segregation of magnetic fields from turbulent motion not only allows strong toroidal fields to accumulate in regions of convect ive overshoot but also permits significant poloidal fields to be maint ained by dynamo action in stars like the Sun.