Simulations of an alpha-effect due to magnetic buoyancy

Three-dimensional simulations of a thermally stably stratified gas with a localized layer of toroidal magnetic field are carried out. The magnetic field gives rise to a magnetic buoyancy instability. Due to the presence of rotation the resulting fluid motions are helical and lead to an -effect, i.e. to a component of the electromotive force in the direction of the mean magnetic field. The value of is estimated during the exponential growth phase of the instability. The mean vertical transport velocity of the magnetic field is also calculated. It is found that varies with latitude and its value is positive in the northern hemisphere.