A theoretical investigation of extraordinary polarized surface
waves at the
second harmonics of ion and electron cyclotron frequencies propagating
across an
external steady magnetic field is carried out in the case of weak plasma
spatial
dispersion when the thermal velocities of plasma particles are much less
than the
phase velocities of the considered waves. These waves are eigenmodes of
a planar
plasma–vacuum waveguide structure that is situated in a steady magnetic
field oriented parallel to the plasma surface. A cold charged-particle
beam is
assumed to propagate over the plasma interface. Excitation of surface X
modes at
the second harmonics of electron and ion cyclotron frequencies due to the
beam–plasma
interaction is studied analytically. The dependence of surface-type X-mode
(STXM) growth rates on the considered waveguide structural parameters is
also
studied.