Low altitude energetic electron lifetimes after enhanced magnetic activity as deduced from SAC-C and DEMETER data

Abstract. When flux enhancements of energetic electrons are produced as a consequence of geomagnetic storm occurrence, they tend to vanish gradually when the magnetic activity calms down and the fluxes decay to quiet-time levels. We use SAC-C and DEMETER low altitude observations to estimate the energetic electron lifetimes (E=0.16–1.4 MeV, L=1.6–5, B=0.22–0.46 G) and compare the decay rates to those observed at high altitude. While crossing the radiation belts at high latitude, the SAC-C and DEMETER instruments sample particles with small equatorial pitch angles (α_eq<18° for L>2.5) whereas the comparison is done with other satellite data measured mainly in the equatorial plane (for α_eq>75°). While in the inner belt and in the slot region no significant lifetime differences are observed from the data sets with different α_eq, in the outer belt, for the least energetic electrons (<500 keV), the lifetimes are up to ~3 times larger for the electrons with the equatorial pitch-angle close to the loss cone than for those mirroring near the equator. The difference decreases with increasing energy and vanishes for energies of about 1 MeV.