Characteristics of auroral proton precipitation observed from sounding rockets

Abstract

A summary of auroral proton observations from 12 sounding rockets launched from Churchill Research Range is presented. Although these rockets were launched into different auroral conditions and at various local times, certain characteristics were observed in all flights. Energy spectra were peaked in the 5- to 10-keV energy intervals with typical intensities near 10$sup 5$ cm$sup -2$ s$sup -1$ sr$sup -1$ keV$sup -1$. Proton pitch angle distributions in the loss cone were isotropic at all energies less than 20 keV. At higher energies, distributions were either isotropic or anisotropic peaked near 90degree pitch angle. Temporal and spatial structure was observed in proton precipitation with typical time scales of the order of 100 equatorial gyroperiods and scale lengths of the order of 100 gyrodiameters. No obvious electron proton correlations were apparent in any of the data. Observations of interactions of the primary proton beam with the neutral atmosphere are presented. Beam spreading effects due to charge exchange interactions are demonstrated, and equilibrium fractions for protons in the atmosphere are measured and compared with relevant laboratory observations. The implication of these results concerning auroral proton source regions and precipitation mechanisms is discussed. (AIP)