ИСТИНА

Recently, in the equatorial topside ionosphere, long-lasting large enhancements of energetic electrons were found. Their significant ionizing effect at low-latitudes and important role in so-called long-duration positive ionospheric storms were asserted. Storm-time contribution from the ionizing effect to ionospheric TEC at low latitudes varies from 10 to 50 TECU depending on a magnetic storm phase. The inner radiation belt (IRB) is a source of these electrons. The trapped energetic electrons of tens of keV energy penetrate to lower altitudes presumably due to a fast radial earthward transport in crossed E and B fields. Simultaneously, the electrons slowly drift eastward, toward the South Atlantic Magnetic Anomaly. The phenomenon of the transient electron injections is not completely understood and hence can not be predicted yet. This study is primarily a prelude to a model of energetic electron enhancements spanning the full solar cycle. Results of statistical analysis of enhancements of >30 keV electrons observed by the NOAA/POES satellites during solar cycles 23 and 24 (1998 – 2016) are presented. It was found that the energetic electron enhancements occur in 25% of time with vast majority at declining phase and solar minimum. The enhancements occur mostly often around midnight in the local time and unexpectedly from May to September in the annual variation. The annual variation results from the changes of the auroral ionosphere conductivity and of the fast solar wind speed.