Observations of Buneman Modes as Precursory Phenomena of a Solitary Potential Pulse

Abstract

A rapidly growing uhf (>250 MHz) wave burst, identified as the Buneman two-stream instability, was detected at the beginning of a high-current plasma discharge. It preceded by nearly 50 ns a parallel electric-field pulse with alternating polarity and amplitude of typically 2.0 kV/cm. A comparison with the nonlinear theory of the Buneman instability showed that the density evacuation mechanism in its nonlinear stage caused a solitary potential pulse within the observed delay time determined by ion dynamics.