Excitation of azimuthal surface waves in the electron cyclotron frequency range by a rotating electron beam in presence of dissipation

Abstract

Azimuthal surface waves are eigen-electromagnetic oscillations which propagate in cylindrical plasma filled waveguides across an axial stationary magnetic field. Their excitation by a flow of electrons which rotate along large Larmor orbits around the plasma column is well studied mostly in the collisionless approach. The influence of weak collisions between the plasma particles on the growth rate of such waves is studied here. Transfer from the mode of beam-plasma instability that takes place in the case of sufficiently high electron beam particle density and weak collisions to that of a beam dissipative instability that occurs if the beam density is low and the collision frequency is sufficiently high is demonstrated.