Variations of Energetic Electron Fluxes in the Ionosphere during Periods of Solar Cycles

Abstract

Energetic electrons (with energies of 10 to 1000 keV) from the Earth’s radiation belt (ERB) play an important role in the processes associated with the ionization of the upper atmosphere and ionosphere from the equator to high latitudes. The main sources and properties of energetic electrons at the altitudes of the ionosphere of up to 1000 km are considered. At high latitudes (more than 50°), precipitations from the outer belt are the sources of such electrons. At low latitudes, intensive fluxes of electrons appear as a result of their injection from the inner ERB. The analysis of the solar-cyclic variation of energetic electron fluxes during two solar cycles in the period from 1998 to 2018 is performed. It is shown that the maximum electron fluxes are most often observed at the declining phases of solar activity (SA), which is associated with the contribution from the recurrent geomagnetic activity. The lowest fluxes are found in the deep minimum of the SA of 2009. As a result, the energetic electron fluxes during the current, 24th, solar cycle are found to be weaker than those in the previous cycle. In addition, an anomalous shift of the position of the maximum of the outer ERB to the equator by 4° (which is equivalent to a distance of 400 km) which is not predicted by the standard model is observed over Siberia. Apparently, this is associated with an acceleration of the change in the geomagnetic field in this region.