Electron precipitation in the postmidnight sector of the auroral zones
Comprehensive measurements of the angular distributions and energy spectra of electron intensities within the energy range 50 eV < or =E< or =15 keV with electrostatic analyzer arrays on board the low-altitude satellite Injun 5 are reported for the postmidnight sector of the auroral zones during the high- intensity events accompanying magnetic substorms. Precipitation features on closed terrestrial field lines well equatorward of the trapping boundary for energetic electrons with E>45 keV are examined. No evidence of maxima in the differential energy spectra or of strongly field-aligned currents, which are indicative of quasi-static electric fields aligned parallel to the geomagnetic field, was found in our series of measurements within the above energy range. Precipitation of low-energy electron intensities fluctuated on time scales of approximately-greater-than2 s as viewed at the satellite position. This precipitation was characterized by isotropy for all pitch angles outside the atmospheric backscatter cone. Maximum precipitated energy fluxes were several ergs. This region of electron precipitation is associated with the diffuse aurora and with pulsating aurora in the postmidnight sector. Similar variations of the energetic electron intensities with E>45 keV were observed in the regions of fluctuating energy fluxes of low-energy electrons associated with auroral luminosity. Precipitation of electron intensities within the energy ranges 50 eV to 15 keV and >45 keV is consistent with strong pitch angle diffusion of electron intensities near or at the magnetic equator by high-frequency wave turbulence, the effectiveness of which is modulated by perturbations attributable to micropulsations to yield the rapid fluctuations encountered over the postmidnight auroral zone. (AIP)
- Research Organization:
- Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-027126
- OSTI ID:
- 4007010
- Journal Information:
- J. Geophys. Res., v. 81, no. 1, pp. 155-167, Other Information: Orig. Receipt Date: 30-JUN-76
- Country of Publication:
- United States
- Language:
- English
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Electron precipitation in the post-midnight sector of the auroral zones. [50 eV to 15 keV]
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Related Subjects
640201* -Physics Research-Atmospheric Physics-Auroral & Ionospheric Phenomena
*AURORAL ZONES- ELECTRON PRECIPITATION
ANGULAR DISTRIBUTION
AURORAE
DAILY VARIATIONS
ELECTRON DENSITY
ENERGY SPECTRA
EV RANGE 10-100
EV RANGE 100-1000
FLUCTUATIONS
FLUX DENSITY
KEV RANGE 01-10
KEV RANGE 10-100
MAGNETIC STORMS
PULSATIONS