Observation of the Farley‐Buneman Instability in laboratory plasma

Abstract

An experiment simulating certain characteristics of the equatorial electrojet plasma (viz. V e »re V i ≳ ri) is described. High frequency (W ≳ V i > ri) instabilities are observed when electrons stream in the E × B direction past ions with a velocity exceeding the ion acoustic speed. The observed phase velocities and frequencies agree with the results of the Farley‐Buneman instability theory, modified to take account of finite k ∥ . The measured instability spectrum for potential fluctuations goes as k −n ⊥ with n = 2–3.5