Turbulence generated by a gas of electron acoustic solitons

Abstract

The characteristics of the electrostatic turbulence generated by a gas of electron acoustic solitons are investigated. Electron acoustic solitons are shown to propagate in magnetized plasmas up to about 30° off the parallel direction without significant changes in their properties relative to the nonmagnetized case. Using the conservation properties of the Korteweg‐deVries equation, the velocity distribution function of the soliton gas is calculated in the small‐amplitude limit. For low cold to hot electron density ratios and high‐mean‐square electric fields, a significant number of solitons with high velocities and amplitudes is produced, implying the generation of an intense broadband electrostatic turbulence. These theoretical results are compared with the properties of the broadband electrostatic noise (BEN) emissions observed by the Viking satellite in the dayside auroral zone. The electric spectra generated by the electron acoustic soliton gases which can be derived from Viking plasma and wave observations are calculated numerically. These spectra are shown to agree with experimental data and in particular to explain the high‐frequency part of BEN emissions, which lies in a range forbidden for linear electrostatic waves.