TEMPORAL VARIATIONS OF OUTER RADIATION ZONE ELECTRON INTENSITIES AT 1 000 km

Publisher Website
Google Scholar
Abstract
The intensities of electrons in the outer Van Allen radiation zone are examined as a function of time using particle detectors on the Alouette 1 satellite. The study covers the period December 1962 to May 1963, during which several moderately large magnetic storms occurred. It is shown that within a few hours after the onset of a magnetic storm the intensity of electrons above 40 keV increases consistently, while the intensity of electrons above 3.9 MeV may decrease and remain low for about a day, or it may remain at prestorm levels for about a day, after which an increase in intensity usually follows. During magnetically quiet periods, electron intensities decay with time constants τ which depend on the particle energy. Typical values of τ are as follows: electrons E > 40 keV at L ~ 6, τ = 4 ± 1 days; E > 250 keV at L ~ 4.7, τ = 6 ± 2 days; E > 3.9 MeV at L ~ 4.3, τ = 14 ± 2 days. Some of the measurements are compared with Explorer 14 measurements which were made at the same time, and significant differences are observed in the behavior of energetic electrons on the same L shells at 1 000 km and near the equatorial plane. For electrons above 40 keV an attempt is made first to relate intensity increases at times of magnetic disturbances to an influx of particles from the "tail" of the magnetosphere and secondly to relate the intensity decreases at magnetically quiet times to a loss of particles into the atmosphere.