Electron Angular Distributions Above the Dayside Auroral Oval.
Abstract
An electrostatic analyzer, a LEPEDEA, was employed on the low-altitude satellite Ariel-4 to gain pitch angle distributions of electron intensities with good temporal resolution within the energy range 205 eV to 12.5 keV over the dayside auroral oval. Two major precipitation zones were encountered--an equatorward zone of broad spectra with intensities of approximately 10,000 electrons/(sq cm-sec-sr-eV) and a poleward zone, the polar cusp, with intensities typical of the magnetosheath. Angular distributions within the equatorward zone are generally isotropic outside of the atmospheric backscatter cone. The precipitation mechanism would appear to be pitch angle scattering near the distant magnetic equator. In contrast, pitch angle distributions within the polar cusp are often found to be strongly field aligned with intensities within the atmospheric loss cone greater by factors of approximately 10 than the mirroring intensities. These angular distributions within the dayside polar cusp are qualitatitively similar to those for the inverted-V precipitation events at later local times, and probably share a common acceleration mechanism with the inverted-V phenomenon.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1975
- Accession Number
- ADA013671
Entities
People
- J. D. Craven
- Louis A. Frank
Organizations
- University of Iowa