Interaction of Test Waves and Trapped Particles in a Collisionless Electron Plasma

Abstract

Theoretical studies are undertaken for effects of interaction between test waves and trapped particles in the presence of a large-amplitude monochromatic plasma wave of field amplitude E₀ and wave number k₀. It is found that the oscillatory variation of the spatial average of the velocity distribution function due to electrons trapped in the wave troughs gives rise to an additional contribution to the plasma polarizability. Furthermore, the trapped electrons induce instabilities of side bands at frequencies ω_k±ω_B, where ω_k is the frequency of a test wave having wave number k and ω_B=(\sqrt2eE₀k₀⁄m)^1⁄2 is the bounce frequency of electrons of charge −e and mass m in the wave troughs of the large-amplitude plasma wave.