ELECTRON-BEAM ACCELERATION BY NONLINEAR LANDAU DAMPING OF ELECTROMAGNETIC-WAVES IN A PLASMA

Acceleration and heating of an electron beam caused by nonlinear Landau damping of intense electromagnetic waves in a plasma are investigated theoretically based on a velocity-space diffusion equation. The beat wave, which does not satisfy the dispersion relation, is excited by the nonlinear interaction of two electromagnetic waves and interacts nonlinearly with the electron beam. As the frequency of the beat wave approaches the electron plasma frequency, the rates of acceleration and heating of the electron beam and the beat wave energy density become maximum values, being equal to those by stimulated Raman scattering. The beat wave is an electrostatic mode that can have a phase velocity near the light velocity and is able to accelerate the electron beam to a relativistic energy.