The Pre-Midnight Asymmetry in the 40 keV Electron Flux Profiles and Its Relation to Magnetospheric Substorms
Passes of the polar orbiting German research satellite AZUR, which are tangential several times per day to the average nightside 40 keV electron flux boundary, often reveal striking asymmetric deviations of the electron flux levels from the average longitudinal or LT distributions. Among these, the most prominent recurrent asymmetric deviation involves an electron flux profile in the dusk-midnight sector which is terminated by a narrow steep spike in the flux of the precipitated and trapped electrons whose location is displaced equatorward from the average boundary (McDiarmid and Burrows, 1968). This phenomenon is probably identical with the’ sharp boundary’ described by McDiarmid and Burrows. Adjacent to the east electron fluxes appear highly structured, more or less poleward of the average boundary location and cover a considerable area in longitude and latitude. A phenomenological description of this phenomenon and of the special features of the orbit of AZUR resulting in the tangential passes appears in Rossberg and Theile (1971), Rossberg (1971). This paper deals with the relation of these asymmetric disturbances to geomagnetic activity.
KeywordsMagnetic Storm Sharp Boundary Electron Flux Satellite Trajectory Dusk Side
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