Fast and ion-cyclotron surface waves at a plasma-vacuum interface

The effect of a finite frequency on the dispersion relation of low-frequency surface waves propagating on a magnetized plasma-vacuum interface is investigated. It is shown that two distinct modes exist depending on the sign of the wavenumber perpendicular to both the magnetic field direction and the normal to the surface, which may be related to the fast and ion-cyclotron body waves. The damping of these waves due to resonance absorption is calculated, and it is shown that the fast surface wave is undamped if its frequency is higher than the ion-cyclotron frequency.