Mappings of energetic electron precipitation following substorms using the satellite bremsstrahlung technique
With an array of collimated cadmium telluride spectrometers on a spinning polar-orbiting satellite (P78-1) a study has been made of the energetic bremsstrahlung X ray (>21-keV) patterns following substorms. From an altitude of approx.600 km, X rays emanating from a wide range of magnetic local times can be observed and the local time profiles mapped on a given pass of the satellite across either polar cap. Pronounced longitude variations in the X ray intensities and hence in the precipitating electron fluxes were observed in the daytime sector at various delay times after the onset of substroms near local midnight. The longitude profile features were found to persist over time periods of at least a few minutes. Longitude variations in the energy spectra of the bremsstrahlung X rays were also obtained, and in several cases the spectra were found to be harder at later local times after midnight, although no consistent trends were evident. Coordinated measurements of electrons from the SCATHA satellite at near-synchronous orbit revealed enhancements in the fluxes of trapped electrons on the dayside at the times of the X ray events, indicating a correlation between the trapped and precipitating electron fluxes. Additional information on the longitude profiles of electron precipitation was obtained from riometer measurements in the Danish chain, which also provided complete time histories at the station longitudes. The longitude distributions of energetic electron precipitation as inferred from satellite X ray intensity and from riometer absorption measurements show very good agreement. The riometer absorption at the Narssarssuaq station with an L value of 7.3, comparable to the SCATHA values, was found to be very similar in time profile to the trapped electron fluxes measured at SCATHA, showing a close association between the trapped and precipitating fluxes of electrons.
- Research Organization:
- Space Sciences Laboratory, Lockheed Palo Alto Research Laboratory, Palo Alto, California 94304
- OSTI ID:
- 5507359
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 87:A2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
MAGNETIC BAYS
ELECTRON PRECIPITATION
BREMSSTRAHLUNG
ELECTRON DENSITY
ENERGY SPECTRA
GEOGRAPHICAL VARIATIONS
TRAPPED ELECTRONS
X RADIATION
CHARGED-PARTICLE PRECIPITATION
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
IONIZING RADIATIONS
LEPTONS
RADIATIONS
SPECTRA
VARIATIONS
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena