FLUCTUATIONS OF INVERTED-V ELECTRON-FLUXES

Fluctuations of low-energy electron fluxes were detected during an inverted V event around 1009 UT, November 5, 1975, by fixed-energy electrostatic analyzers onboard the AE-D satellite. The flux fluctuations were observed at energies of 0. 72, 1. 38, and 2. 62 keV when these energies were below that of the monoenergetic beam, suggesting that the flux fluctuations might occur over a wide range of energies. The fluctuations were confined within a pitch angle of 15 degree , and the amplitude increased with decreasing pitch angles. The oscillation frequencies centered around 1. 75 Hz. The fluctuations at two energies were generally correlated. From the variation of the distribution function with respect to the distribution function at 0. 72 keV we deduce that secondary electrons were heated. The author's interpretation of these observations is that the secondaelectrons were heated anomalously by electron plasma wave turbulences and that the intensity of the wave turbulences was modulated by a low-frequency wave. These results are consistent with the model that auroral precipitating electron beams enhance the anomalous resistivity at the topside ionosphere through parametric instabilities.