Pitch angle diffusion coefficients and precipitating electron fluxes inferred from EISCAT radar measurements at auroral latitudes

摘要

Theoretical predictions of the generation of precipitating fluxes of energetic electrons by pitch angle scattering by whistler waves are made using the quasi-linear theory of wave-electron interaction from Kennel and Petschek [1966] and trapped electron spectra obtained from geosynchronous satellites during nine auroral absorption events. Cyclotron instability spatial growth rates are found to exceed the critical value needed for spontaneous generation of whistler mode waves in the morning and noon local time sectors in all events. Where available, conjugate observations (by the European Incoherent Scatter (EISCAT) UHF radar) of electron density disturbances produced in the ionosphere are used to determine the fluxes of precipitating electrons with E greater than or equal to 30 keV and to estimate the required magnitudes of the pitch angle scattering. These are found to lie in the transition region between weak and strong diffusion regimes. Further, it becomes clear that changes in precipitation during the course of individual absorption events are primarily due to changes in the,strength of the diffusion process occurring. [References: 39]