Hydromagnetic surface waves with alternating magnetic fields

Abstract

Hydromagnetic surface waves propagating on the surface of a finitely conducting fluid are studied experimentally and theoretically. An alternating magnetic field is used, so that the field is largely excluded from the bulk of the fluid. Thus, the magnetic damping of the waves is negligible, and the perfectly conducting d.c. case is simulated. The effects of a finite electromagnetic skin depth, δ, are included in the calculation of the theoretical wave dispersion relation. It is predicted that as δ is increased and becomes comparable to the wavelength of the surface wave, the effect of the magnetic field on the fluid motion is decreased. This prediction is confirmed experimentally.