TURBULENCE GENERATED BY A GAS OF ELECTRON-ACOUSTIC SOLITONS

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