Temporal behavior of energetic particle precipitation during an auroral substorm

Abstract

Results from two rocket experiments launched from Fort Churchill Research Range into the breakup and post-breakup phases of an auroral substorm are described. Unusual characteristics were observed in energy spectra and pitch-angle distributions of energetic electrons (E> 3 kev) and protons ( >28 kev) simultaneously with the arrival of the northern edge of a series of northward-propagating auroral arcs. When the northern edge passed the rocket, electron intensities increased and the spectrum hardened appreciably, both changes occurring with time constants less than about 2 seconds. Dispersion in arrival times of electrons was observed with the low-energy particles arriving first. After the initial injection the particle fluxes were observed to decay at rates consistent with the maximum decay rates for these latitudes. Decay times of the order of a few minutes for electrons and a few hours for protons were observed. Electron angular distribution characteristics were found to be energy dependent. The recovery-phase of the substorm was found to be characterized by soft isotropic electron precipitation.