ISEE-1 OBSERVATIONS OF ELECTROSTATIC ION-CYCLOTRON WAVES IN ASSOCIATION WITH ION-BEAMS ON AURORAL FIELD LINES FROM APPROXIMATELY 2.5 TO 4.5 RE

Quasi-monochromatic waves at approximately 1.2 f(cH) where f(cH) is the hydrogen cyclotron frequency, were observed as the ISEE 1 satellite traversed auroral field lines at radial distances of approximately 2.5-4.5 R(E) near midnight on June 19, 1981. The waves were Polarized perpendicular to the magnetic field (k parallel-to/k perpendicular-to less-than-or-similar-to 0.2). In addition, there were waves at slightly above both the helium and the oxygen cyclotron frequencies. The waves occurred within a region of reduced density (approximately 0.1-0.2/cm3) with the electron temperature greater than the ion temperature, upflowing hydrogen and oxygen beams, and weak field-aligned currents bounded by electrostatic shocks. The wave characteristics and associations were similar to those observed at lower altitudes by the S3-3 satellite. Comparisons were made between the observed H+ and O+ beams, field-aligned currents, densities and temperatures, and linear theories of electrostatic ion cyclotron waves and H+-O+ two-stream instabilities. The features of the observed waves are most consistent with the current-driven mode. In addition, numerical studies of the linear dispersion relation, using parameters based on the observations, showed that both the parallel and oblique two-stream modes and the ion-beam driven modes were stable while oblique current driven modes were unstable. The O+ and H+ distributions provide evidence for interactions with local electrostatic ion cyclotron waves and for the H+-O+ two-stream instability altitudes below the satellite.