Ponderomotive effects in nonneutral plasmas

Abstract

The ponderomotive effects which arise in a single species plasma, i.e., a nonneutral plasma, are considered. The important difference from a neutral plasma is that quasineutral density cavities given by δn/n0≂−‖E‖2/16πn0T cannot arise in a single species plasma. Instead, it is found that the ponderomotive force is balanced by self-consistent space charge fields, and results in δn≂∇2‖E∥‖2/16πmω2, where ω is the frequency and E∥ refers to the wave electric field parallel to the confining magnetic field. In addition to the density rearrangement, the zero order E×B rotation is modified. The self-consistent nonlinear state has been found for a large-amplitude l=0 axially standing Gould–Trivelpiece wave. The linear dispersion relation is modified by the presence of the large-amplitude wave and results in a nonlinear frequency shift. This shift produces an interesting hysteresis effect in the nonlinear resonant response of the plasma when the frequency of the external driver is swept slowly.