The Day‐night Difference and Geomagnetic Activity Variation of Energetic Electron Fluxes in Region of South Atlantic Anomaly

Abstract : Utilizing the DEMETER observations at 670km, we examined the day‐night difference of energetic electrons (100 – 800keV) in the South Atlantic Anomaly (SAA) region and their dependence on geomagnetic activities in different seasons. Under geomagnetically quiet conditions, the fluxes of higher‐energy electrons (> 200keV) in the dusk and midnight (MLT ~ 19 – 24hr) are usually larger than those in the morning (MLT ~ 8 – 12hr) in the core region of the SAA (−50 ≤ λ ≤ − 20deg) during the northern and southern summers (21/03/2007 – 23/09/2007 and 23/09/2007 – 21/03/2008). The day‐night difference of energetic electrons in SAA region depends not only on the electron energy but also on the geomagnetic activity levels. Enhanced geomagnetic activities increase the energetic electrons in morning and hence weaken their day‐night difference in the SAA region.