Effect of hall current on hydromagnetic instability of a couple-stress ferromagnetic fluid in the presence of varying gravitational field through a porous medium

Abstract

The effect of hall current on hydromagnetic instability of a couple-stress ferromagnetic fluid in the presence of variable gravity field through a porous medium is determined. We have used a linear stability theory and normal mode technique to discover the precise solution for a layer of couple-stress ferromagnetic fluid contained between two free boundaries. For the case of stationary convection, we have found that medium permeability, couple-stress, magnetic field and hall current have both stabilizing and destabilizing effect under certain conditions. Also, magnetization has a stabilizing effect on the system. Graphs in each case have been plotted by giving numerical values to these parameters. In the absence of magnetic field (hence hall current), the principle of exchange of stabilities is found to hold true under certain conditions.