Surface waves at a plane interface between vacuum and plasma with the magnetostatic field normal to the interface

The characteristics of the surface waves sustained by a plane interface which separates semi-infinite regions of vacuum and magnetoionic medium are investigated for the case in which the magnetostatic field is normal to the interface. It is found that plane surface waves exist if the gyromagnetic frequency is less than the plasma frequency and in the range of frequencies lying between the gyromagnetic frequency and
1/\sqrt{2}
times the upper hybrid resonant frequency. The phase velocity of the surface waves is always less than the velocity of electromagnetic waves in free space, and it decreases monotonically with the increase in the frequency and goes to zero at
1/\sqrt{2}
times the upper hybrid resonant frequency.