Modeling energetic electron precipitation near the South Atlantic anomaly

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 less than or equal to 2, the flux of electrons precipitated into the atmosp here is strongly localized to a longitudinal range (+/-15 degrees) centered near the South Atlantic anomaly (SAA), where the surface magnetic field in tensity is weakest and the bounce loss cones are exceptionally large. For r ealistic average rates of pitch angle scattering, the energy deposition rat es, obtained from the modeled precipitation flux patterns, yield peak ioniz ation 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 pre cipitating electrons should be a prominent mesospheric ionization source ne ar the SAA but relatively insignificant elsewhere.