Global distribution of energetic proton precipitations equatorward of the boundary of isotropic fluxes

Abstract

Based on data of the NOAA POES satellite, the global distribution of the occurrence rate of precipitations of energetic protons (E > 30 keV) equatorward of the boundary of isotropic fluxes has been constructed for the first time. It has been shown that the occurrence rate of proton precipitations inside the zone of anisotropic fluxes is maximum in daytime hours (1100–1600 MLT) at latitudes L = 6–9 and decreases in evening and morning hours. Comparison of the obtained results about proton precipitations with the spatial distribution of the occurrence rate of electromagnetic ion–cyclotron (EMIC) waves in the equatorial magnetosphere according to results of satellite observations demonstrates a close relationship between them. This corroborates that precipitations of energetic protons equatorward of the boundary of isotropic fluxes are a consequence of the development of the ion–cyclotron instability in the equatorial magnetosphere.