Abstract
This work examines the Benard convection of an infinite horizontal layer occupied by a porous medium permeated by an incompressible, thermally and electrically conducting viscous fluid heated from below when subjected to both uniform vertical magnetic field and Coriolis forces. A model proposed by P. H. Roberts (1981) in the context of neutron stars is used. We show that the nonlinerity in this model has no effect on the development of instabilities through the mechanism of stationary convection which is the preferred process in terrestrial applications. However, in non-terrestrial applications the non-linearity influences the onset of overstable convection and overstability is the preferred mechanism. Some numerical results are presented for the overstability case when both boundaries are free and rigid.