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 temper ature enhancements recorded from the DE-2 satellite are presented. Fou r different wave events were analyzed, all recorded at magnetic latitu des from 57-60-degrees, magnetic local times from 8-14 hours, and alti tudes from 600-900 km. The peak wave amplitudes during the events rang ed from 870 nT and 5-30 mV/m in the magnetic and electric field, respe ctively. Electron temperature (T(e)) enhancements at the time of the w aves 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 e nhanced flux of low energy electrons. During one event (82104) an enha nced flux of electrons were observed at energies up to 50eV and at nea rly all pitch angles, although the flux was largest in the precipitati ng and upflowing directions. It is suggested that the waves are respon sible for heating the low energy electrons which precipitate to the io nosphere and produce the observed T(e) enhancements. The upflowing ele ctron 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 observation s do not rule out electron heating near the equator.