A mean electromotive force induced by magnetic buoyancy instabilities

For a variety of reasons, based on results from magnetoconvection, self-con sistent dynamo calculations and helioseismology, it seems plausible that th e bulk of the solar magnetic field is located in the overshoot zone. Furthe rmore, it has also been suggested that the solar dynamo is operating in thi s region. The aim of this paper is then to show that it is possible to obta in a mean electromotive force (EMF), and hence an alpha-effect, in the conv ectively stable overshoot zone, which is driven by magnetic buoyancy instab ilities. By investigating the stability of a layer of magnetic field embedded betwee n two non-magnetic layers of plasma we are able to show the following: firs t, that magnetic buoyancy instabilities indeed give rise to a mean EMF and, secondly, that the electromotive force is largest in the region where the magnetic layer is unstable, i.e. where the field strength decreases fastest with height. Moreover, the influence of the rotation rate and the magnetic field strengt h on the magnetic buoyancy instability has been investigated in order to de termine for which values of these parameters dynamo action might occur.