Nonlinear Interaction of Bernstein Waves in a Beam-Plasma System

Abstract

Bernstein waves (Electron Cyclotron Harmonic Waves) are observed to excite and grow exponentially in distance up to saturation levels, and then damp slowly when a gyrating electron beam is injected into a plasma in a thermal equilibrium. As the beam becomes intense, there appear the harmonics of the Bernstein waves ascribed to a nonlinear interaction of these waves. In accordance with an increase of the emission power of harmonics, widths of these harmonics become broad and then their spectra become continuous, showing that they resemble closely the turbulence spectra.
The experimentally observed characteristics of the Bernstein waves are very similar with those of Landau waves and have close correlations with the beam-plasma discharge.