Electron precipitation near L=4: Longitudinal variation

Abstract

Observations of penetrating electron precipitation at two L ∼ 4 stations in the southern hemisphere, Kerguelen and Siple Station, Antarctica, are summarized. The nearly complete absence of precipitation at Kerguelen and its frequent occurrence at Siple Station is explained in terms of their location with respect to the center of the South Atlantic geomagnetic anomaly at L ∼ 4. Conclusions which result from this explanation are discussed along with questions which remain concerning penetrating electron precipitation.