PARAMETRICALLY DRIVEN SURFACE-WAVES ON VISCOUS FERROFLUIDS

Standing waves on the surface of a ferrofluid in a normal magnetic fie ld can be excited by a vertical vibration of the container. A stabilit y theory for the onset of these parametrically driven waves is develop ed, taking viscous dissipation and finite depth effects into account. It will be shown that a careful choice of the filling level permits th e normal and anomalous dispersion branches to be measured. Furthermore it will be demonstrated that the parametric driving mechanism may lea d to a delay of the Rosensweig instability. A bicritical situation can be achieved when Rosensweig and Faraday waves interact. [S1063-651X(9 8)05311-2].