Spatial and Temporal Variations of Proton Fluxes in the Earth’s Inner Radiation Belt during a Solar Cycle

The results are presented from an analysis of proton fluxes in the inner radiation belt (RB), obtained with the ARINA spectrometer. The ARINA satellite experiment was performed on board the Russian low-orbit spacecraft Resurs-DK1 (altitude 350–600 km; inclination 70°; duration, 2006–2016). The spectrometer registered high-energy protons (30–100 MeV) with an energy resolution of 10% and an angular resolution of 7°. The geographical and pitch-angle distribution of proton flux in the inner radiation belt (1.15 < L < 2.0) were analyzed during the waning phase of the 23rd solar cycle and main part of the 24th cycle. It is shown that the proton flux intensity depends on the phase of the solar cycle (the minimum intensity is observed in the period of the solar activity maximum and vice versa) and varies by 2–7 times for different L‑shells.