LOCALIZED INJECTION OF LARGE-AMPLITUDE PC-1 WAVES AND ELECTRON-TEMPERATURE ENHANCEMENT NEAR THE PLASMAPAUSE OBSERVED BY DE-2 IN THE UPPER IONOSPHERE

The relation between electron temperature enhancement and large amplit ude Pc 1 wave injections in the upper ionosphere is investigated using the data obtained by the Dynamics Explorer 2 spacecraft. Results can be summarized as follows: (1) The region of the temperature enhancemen t coincides with that of the wave injection which is latitudinally ver y narrow (< 100 km) in comparison with the wavelength along the ambien t magnetic field (several hundred kilometers). (2) The duration of the wave injection (or the temperature enhancement) seems to be less than a few hours even under quiet geomagnetic conditions, and/or the injec tion seems to be very localized, not only latitudinally, but also long itudinally. (3) The appearance and the magnitude of temperature enhanc ement depend on both the wave amplitude and the satellite altitude. (4 ) Two of the 22 events that were analyzed show a clear enhancement of low-energy electron flux (5-30 eV) at the wave injection, and the flux is field-aligned both downward and upward. The region of the temperat ure enhancement coincides with that of the downward electron flux. Fro m these results, it is suggested that the temperature enhancement whic h accompanies large-amplitude waves with Pc 1 pulsation frequencies (0 .2-5 Hz) is caused by the direct acceleration of thermal electrons at low altitudes by the parallel electric field (0.01-0.001 mV m-1) of th e ion-cyclotron waves (kinetic Alfven waves) having an oblique wave no rmal.