Electromagnetic plasma modes at ωpe

The problem of the electromagnetic plasma radiation near the electron plasma frequency ω_pe is studied in the absence of an external magnetic field. Maxwell´s equations together with the fluid equations, which include thermal effects, are solved for an infinite geometry as well as for a finite geometry, and the problem of the eigenmodes at a plasma frequency ≈ ω_pe is studied. The excitation of these modes by a small density relativistic beam is discussed. It is shown that the presence of a small density beam with finite u_o/c (where u_o/ is the beam velocity and c the velocity of light in a vacuum) in a plasma of finite thermal velocity, can couple linearly the plasma oscillations excited by the beam with the electromagnetic plasma mode at ω_pe. It is also shown that surface waves at a frequency ≈ ω_pe can be excited by the beam.