ELF PLASMA-WAVES IN HOT AND COLD-PLASMA FLUXES OBSERVED BY PROGNOZ-8 IN THE MAGNETOSPHERIC TAIL

We present Prognoz-8 observations of low-frequency plasma waves (2-105 Hz) associated with plasma fluxes near the outer boundary of the plas ma sheet. These plasma fluxes were different from the regular plasma s heet boundary layer and consisted of tail-ward flowing warm proton and cold oxygen beams accompanied by rather cold electrons (T-e less than 100 eV). Observed plasma characteristics were used in the numerical s olution of the dispersion relation for the ion-beam acoustic instabili ty. Detailed analysis shows that this instability can be a source of o bserved emissions as frequencies up to 25 Hz.