MEAN-FIELD MAGNETIC BUOYANCY IN A TURBULENT MEDIUM

Magnetic buoyancy is studied using mean field magnetohydrodynamics. Th e surfacing velocity is a nonmonotonic function of the magnetic energy density. Initially it increases with field strength, but then diminis hes for strong fields. The latter is caused by magnetic tension Which has usually been ignored in earlier studies of magnetic flux tube buoy ancy. The buoyancy saturation effect at strong fields substantially we akens the restriction imposed by buoyancy on cosmic dynamo models. The buoyancy rise time from the bottom to the top of the solar convection zone is at least 6 years for fields of arbitrary strength.