The east-west asymmetry of the ionospheric electron content in south Atlantic geomagnetic anomaly region

The Ionospheric Electron Content (IEC) in the South Atlantic Geomagnetic Anomaly (SAGA) has been investigated by means of the Faraday rotation technique with the use of the VHF signal emitted from the ATS-6 radio beacon satellite during the east-west movement. The measurements were carried out at Atibaia, (46°33′W, 23°11′S) and show an increase of ~50% on the west side of the receiver in relation to the east side, principally during the night period. We suggest that this asymmetry is caused by low energy electrons ( E < 40 keV) precipitated during their longitudinal drift.