SIMULTANEOUS OBSERVATIONS OF SUBAURORAL ELECTRON-TEMPERATURE ENHANCEMENTS AND ELECTROMAGNETIC ION-CYCLOTRON WAVES

Observational results from an investigation of low frequency (0.5-4.0 Hz) electromagnetic ion cyclotron waves and subauroral electron temperature enhancements recorded from the DE-2 satellite are presented. Four different wave events were analyzed, all recorded at magnetic latitudes from 57-60-degrees, magnetic local times from 8-14 hours, and altitudes from 600-900 km. The peak wave amplitudes during the events ranged from 870 nT and 5-30 mV/m in the magnetic and electric field, respectively. Electron temperature (T(e)) enhancements at the time of the waves were observed in 3 of 4 events. A linear relationship between the wave magnetic field spectral density and T(e) enhancements was found for these events. The T(e) enhancements were also correlated with an enhanced flux of low energy electrons. During one event (82104) an enhanced flux of electrons were observed at energies up to 50eV and at nearly all pitch angles, although the flux was largest in the precipitating and upflowing directions. It is suggested that the waves are responsible for heating the low energy electrons which precipitate to the ionosphere and produce the observed T(e) enhancements. The upflowing electron population appears to be heated at ionospheric altitudes, below the DE-2 satellite. The precipitating electrons may also be heated at ionospheric altitudes through Landau damping, although the observations do not rule out electron heating near the equator.