Dispersion characteristics of surface waves in a semibounded plasma
flow with relativistic velocity u0 parallel to the plasma–vacuum interface are
presented. The plasma is considered to be cold and collisionless, which allows us
to take into account only the electron motion. It is shown that – in contrast to
the bulk waves, which are invariant with respect to Lorentz transformations
and whose spectrum is independent of the flow velocity – the surface waves are
not invariant, which leads to a dependence of their spectrum on the flow
velocity and, correspondingly, to non-reciprocity. The latter peculiarity is due
to the fact that the boundary conditions are not invariant.