Abstract:
South Atlantic Magnetic Anomaly (SAMA) due to its weak total geomagnetic field F is known to be a sink of trapped charged particles from the inner radiation belt during both magnetically quiet and disturbed periods. Ionosondes, riometers, and VLF radio propagation monitoring experiments have shown ionospheric effects due to increase of ionization caused by the process of electron precipitation in the ionosphere of SAMA region during the quiet and disturbed periods. We have examined the records of geomagnetic horizontal component variations at the time of sudden commencement (SC) from two stations, Sao Martinho da Serra (SMS) (29:43S, 53:82W, 19:0 geomagnetic latitude and 33dip) and Vassouras (VSS) (22 :40S, 43 :65W, 16:7 geomagnetic latitude and 33dip), both situated in the SAMAregion at nearly the same magnetic latitude. The SCðHÞ amplitudes in general are found to be larger at SMS situated close to the center of SAMA, compared to the ones found at the station VSS situated away from the center of SAMA. The results seem to provide an evidence that the amplitude enhancements of the SCðHÞ impulse in the SAMA region could be caused by the differential increase of ionization due to the continuous loss of electrons and ions from the magnetosphere into the atmosphere of SAMA region.
