Boundary Effect on the Frequency of an Ion Acoustic Wave in an Ion-Beam Plasma System

Abstract

The frequency change of an ion acoustic wave by the finite boundary effect is examined experimentally and theoretically for an ion-beam plasma system. The ion acoustic and its harmonic-like waves can be excited by the finite boundary effect though the condition for the occurence of the usual two stream instability is not satisfied in an unbounded case. The frequencies of these waves decrease monotonically with the distance between two boundaries. Their frequencies change slightly by altering either the number density or the drift velocity of the ion beam. These characteristics are well explained by a dispersion relation derived from the linearized one-dimentional fluid equations on the boundary condition.