Diffusive instabilities in magnetohydrodynamic convection

Abstract

The role played by diffusion in destabilizing dynamically stable fluid flows is reviewed. The resistive instabilities, to which a rapidly rotating Bénard layer lying in a uniform magnetic field is prone, are described. It is shown that diffusivity of heat and field permits convection that would be forbidden in their absence. When the model is generalized to spherical systems and to non-uniform fields a new, even more unstable, mode will occur provided the magnetic diffusivity is sufficiently small (though non-zero).