Study of Nonlinear Electron Beam-Plasma Interaction Based on the Generalized Weak Turbulence Theory

Abstract

Harmonic Langmuir waves and multiple harmonic plasma emission are interesting nonlinear phenomena that take place during the electron beam-plasma interaction process. It is difficult to explain these nonlinear phenomena within the framework of the customary weak turbulence theory, so we put forth a theoretical explanation in the framework of the "generalized" weak turbulence theory. On the basis on the wave kinetic equation governing the interaction of a transverse electromagnetic (EM) wave with nonlinear harmonic Langmuir waves, it is found that an EM wave with a frequency in the vicinity of higher harmonics of the plasma frequency is amplified as a result of a nonlinear wave-wave interaction between the EM and the harmonic Langmuir waves. The dependency of the EM emission at higher harmonics on the angle defined with respect to the beam's propagation direction is numerically examined by modeling the harmonic Langmuir wave spectrum.