EFFECT OF VARIABLE GRAVITATIONAL-FIELD ON THERMAL-INSTABILITY OF A ROTATING FLUID LAYER WITH MAGNETIC-FIELD IN POROUS-MEDIUM

The effect of variable gravitational field on thermal instability of a rotating fluid layer in the presence of magnetic field in porous medi um is investigated. It is found that the system is stable when gravity is decreasing upwards. The principle of exchange of stability is vali d in the absence of rotation and magnetic field when gravity increases upwards. In the stationary convection, rotation has stabilizing or de stabilizing effect depending upon whether gravity is increasing or dec reasing upwards. The medium permeability and magnetic field have stabi lizing or destabilizing effect depending upon condition.