Modeling energetic electron precipitation near the South Atlantic anomaly

Abstract

A numerical simulation of electron pitch angle scattering in an asymmetric magnetic field environment has been applied to the Earth's inner radiation belt to obtain a global pattern of energetic electron precipitation. Under conditions of weak pitch angle scattering, which characterize the region L ≤ 2, the flux of electrons precipitated into the atmosphere is strongly localized to a longitudinal range (±15°) centered near the South Atlantic anomaly (SAA), where the surface magnetic field intensity is weakest and the bounce loss cones are exceptionally large. For realistic average rates of pitch angle scattering, the energy deposition rates, obtained from the modeled precipitation flux patterns, yield peak ionization rates in the middle mesosphere (near 75 km) between 0.1 to 1 ions cm −3 s −1 over the L range 1.35–1.95, respectively. This indicates that precipitating electrons should be a prominent mesospheric ionization source near the SAA but relatively insignificant elsewhere.