Energetic electron components at geosynchronous orbit

Abstract

Energy distribution functions have been derived from energetic (30–2000 keV) electron fluxes observed simultaneously by three geosynchronous orbit satellites throughout the year 1986. These distributions, as well as others derived from empirical models of outer magnetospheric electron fluxes, can be resolved into two distinct relativistic Maxwellian components which are each fully parameterized by a density and a temperature. The resulting four‐parameter model of magnetospheric energetic electrons yields the following results: Higher energy (300–2000 keV) “hard” electrons are characterized by Th ≃200 keV and nh ∼ 10−4 cm−3; nh decreases during substorms, but Th shows very little change on a substorm (hourly) time scale. Lower energy (30–300 keV) “soft” electrons have nominal parameter values Ts ∼25 keV and ns ∼ 5 × 10−3 cm−3; intense substorm‐related injections and extreme temporal variability characterize this component. This four parameter characterization presents a new, simplified procedure for the interpretation of energetic electron data in the outer magnetosphere.