Comparative Observations of the Outer Belt Electron Fluxes and
Precipitated Relativistic Electrons
Abstract
Relativistic electron precipitation (REP) refers to the release of high
energy electrons initially trapped in the outer radiation belt that
precipitate into the Earth’s upper atmosphere. REP plays an important
role in the magnetosphere as it contributes to the fast depletion of
radiation belt electron flux. This study presents a statistical analysis
of the REP observations made by the Calorimetric Electron Telescope
(CALET) experiment on board the International Space Station (2015-
present). Specifically, a catalog based on count rates from the two top
scintillators constituting the top charge detector, sensitive to
electrons with energies $>$1.5 MeV and
$>$3.4 MeV, respectively. Data from the CALET experiment
reveals a previously unreported semi-annual variation in the occurrence
of REP events. The REP periodicities are similar to those observed for
trapped electrons in the outer belt, and correlates with the occurrence
of solar wind high-speed streams and the solar cycle variations.