Instability of two rotating oldroydian viscoelastic superposed fluids through porous medium

The instability of the plane interface between two Oldroydian viscoelastic superposed fluids through porous medium in the presence of uniform rotation and variable magnetic field is discussed. The magnetic field, the viscosity and the density are assumed to be exponentially varying. For stable density stratification, the system is found to be stable for disturbances of all wave numbers. The magnetic field stabilizes the potentially unstable stratification for small wave-length perturbations which are otherwise unstable. The long wavelength perturbations remain unstable and are not stabilized by magnetic field. Rotation does not affect the stability or instability, as such, of stratification.