Features of quasi-stationary precipitations according to the data obtained with the AVS-F instrument onboard the CORONAS-F satellite

Abstract

In the absence of burst events, the typical count-rate temporal profile of the AVS-F instrument in the low-energy gamma-ray band has a single broad maximum in the geomagnetic-equator region at latitudes from −30° to +40°). However, the so-called quasi-stationary precipitations, i.e., increases in the count rate by up to 15–30% with respect to the average level determined using polynomial fits, were observed in some equatorial regions at latitudes from −25° to +30°. At least four (type I, II, III, and IV) groups of such events can be distinguished according to their temporal profiles. The temporal profiles of about 44% events show a rapid increase to the south from the geomagnetic equator and a gradual decrease in the northern direction. For about 21% of analyzed events, on the contrary, the count rate increases sharply to the north of the geomagnetic equator and decreases gradually to the south. About 4% of events have symmetric temporal profiles. Finally, another 4% of the detected events have the form of a significant (a factor of 1.3–1.8) increase in the count rate with a central maximum. Typical durations of precipitations are 7–10 min (the size of the precipitation region is 20°–35°). However, short events lasting for ∼3 min (the size of the precipitation region is ∼10°) were observed. The mean time interval in which the precipitations were observed in regions with dimensions of 10° in geographic latitude by 30° in geographic longitude was about 24 h (the maximum interval exceeded 8 days). The majority of precipitations were observed in a zone of width 40° centered at the geomagnetic equator. Quasi-stationary precipitations can be related to the precipitations of charged particles in certain regions of the Earth’s magnetosphere periodically crossed by the satellite.