Gaussian Laser Beam in a Magnetized Plasma

Abstract

A narrow electromagnetic beam propagating parallel to anexternal magnetic field in a plasma is considered theoretically. Thetheory assumes that the plasma pressure is larger than theelectromagnetic one. It is found that under the paraxial approximationthe beam having a Gaussian cross section can propagate. The Rayleighrange is enlarged or shortened depending on the dielectriccoefficients of the plasma. The beam is either right- or left-handpolarized and both modes have the longitudinal component of theelectric field as the Gaussian beam does in vacuum. The phasevelocities can become less than the light velocity c for some plasmaparameters for which those velocities of the plane R- and the L-wavesare always greater than c.