Excitation of Ion-Acoustic Waves

Abstract

The excitation of ion-acoustic waves by a pair of idealized grids in a collisionless plasma is examined. It is shown that in a limited region, neither too close nor too far from the source, the disturbance closely approximates an exponentially damped (spatially) ion-acoustic wave. Far from the source a weak electron "wave" with less damping and larger wavelength dominates; near the source the potential varies as $\frac{1}{z}$.