OBSERVATIONS OF AN UPWARD-DIRECTED ELECTRON-BEAM WITH THE PERPENDICULAR TEMPERATURE OF THE COLD IONOSPHERE

The Freja TESP electron spectrometer has repeatedly observed similar t o 100 eV - 1 keV upward-directed, anti-field-aligned electron beams ne ar 1700 km altitude in the auroral zone. A particularly intense event, at energies up to 2 keV, is described. The beam perpendicular tempera ture T perpendicular to(e)), was as low as 0.1-0.2 eV at 100-200 eV pa rallel energy. The 10-15 s period of upward fluxes was coincident with a low density (similar to 10 cm(-3)) period and a similar to 5 keV io n conic. Strong low frequency waves and the lack of any downward motio n in the simultaneously observed ion conic suggest a strong element of wave acceleration, while electric field and ion loss cone measurement s provide limited evidence of potential acceleration to a fraction of the observed energies.