By using balloon X ray and electric field measurements [Gonzalez et al., 1982; Pinto and Gonzalez, 1986”, it has been suggested [Gonzalez et al., 1987] that localized relativistic electron precipitation seems to occur at the South Atlantic Magnetic Anomaly (SAMA) during the recovery phase of intense geomagnetic storms. Those measurements were obtained from balloons launched at Brazilian sites.
This type of precipitation seems to consist of narrow latitudinal bands, localized at low L values, where precipitation tends to be enhanced. Candidate processes to explain its origin are cyclotron resonances of inner-belt relativistic electrons with plasmaspheric hiss [Gonzalez et al., 1987; Pinto and Gonzalez, 1988]. These waves have been shown to exist predominantly during the recovery phase of storms and to have density peaks at very low L values, off the equator [Tsurutani et al., 1975], right at the latitudes that correspond to the balloon measurements.