Physics of auroral phenomena : proceedings of the 37th Annual seminar, Apatity, 25 - 28 February, 2014 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Изд-во Кольского научного центра РАН, 2014. - 125 с. : ил., табл.

Relativistic electron precipitation as seen by NOAA POES always situated equatorward of that for electrons because the gyroradius of the 30-keV proton is larger than that of the ~1 Mev electron. During the time interval under study, 65 such events (or 31% of all REP events) are found. The second group consists of REP spikes, which coincide with the enhanced precipitation of >30 keV electrons and do not coincide with any proton precipitation enhancement (Fig. lb). These REP are observed well within the anisotropic zone of relativistic electrons and on both sides of the isotropy boundary o f 30-80 keV protons. This group consists of 117 events (56%). Finally, there is a group of REP events, which coincide with localized spikes of precipitation of 30-80 keV protons (Fig. lc). These events occur within the anisotropic zone o f relativistic electrons and always equatorward of the isotropy boundary of 30-80 keV protons. Only 27 such events (13% of all REP events) were observed. In Fig. 2 a map of REP events is shown in the MLT-CGLat coordinates. The majority o f REP events is observed at 60°-70° CGLat. The events of the first group are observed around midnight (20-03 MLT) (Fig. 2a). The events of the second group are seen in all MLT, but mainly in the evening and midnight sector (Fig. 2b). The events correlated with the proton precipitation spikes are observed within the 14-23 MLT interval (Fig. 2c). The occurrence of the REP events mapped onto the equatorial plane is shown in Fig. 3. The occurrence is determined as the ratio of a number of satellite crossings with REP observations to a number of all crossings through a given region (a cell with dimensions equal to 1 R e of the distance from the Earth and 1 hour of MLT). The maximal occurrence of the REP events of the first and second groups is some 5 % (Fig. 3a,b), and the events of the third group have maximal occurrence as low as -1% (Fig. 3c). a b с Figure 2 Figure 3 4. Discussion In some extent, three types of relativistic electron precipitation described above have been studied in earlier works (see, Introduction). Similar study has been made by Imhofet al. (1986, 1991) who also used data from oolar-orbitine low-altitude satellites. Im ho fet al (1991) studied REP events at the trapping boundary, which w e I s s u e d 7 s 48