Convective instability of magnetized ferrofluids

Convective instability in a flat ferrofluid layer subject to a transverse uniform magnetic field is investigated theoretically. A temperature gradient imposed across the layer induces a concentration gradient of magnetic grains owing to the Soret effect. Both these gradients cause a spatial variation in magnetization that establishes a gradient of magnetic field intensity within the fluid layer. The field gradient induces in its turn a redistribution of magnetic grains due to magnetophoresis. The resulting self-consistent magnetic force tries to mix the fluid. Linear analysis performed for the case of realistic boundary conditions on confined horizontal planes predicts double-diffusive oscillatory instability in a certain region of parameters, whereas if the particle diffusion had been not operative, then only stationary instability would occur.