Electron Acoustic Waves in Pure Ion Plasmas

Abstract

Electron Acoustic Waves (EAWs) are the low frequency branch of electrostatic plasma waves. These waves exist in neutralized plasmas, pure electron plasmas and pure ion plasmas. At small amplitude, EAWs have a phase velocity vph≃1.4 v and their frequencies are in agreement with theory. At moderate amplitudes, waves can be excited over a broad range of frequencies and their phase velocity is in the range of 1.4 v⩽vph⩽2.1 v. This frequency variability comes from the plasma adjusting its velocity distribution so as to make the plasma mode resonant with the drive frequency. These plasma waves can also be excited with a chirped frequency drive resulting in extreme modification of the particle distribution, giving almost undamped waves with (γ/ω∼10−5).