Distribution of Earth's radiation belts' protons over the drift frequency of particles

Abstract. Using data on the proton fluxes of the Earth's radiation belts (ERBs) with energy ranging from 0.2 to 100 MeV on the drift L shells ranging from 1 to 8, the quasi-stationary distributions over the drift frequency fd of protons around the Earth are constructed. For this purpose, direct measurements of proton fluxes of the ERBs during the period from 1961 to 2017 near the geomagnetic equator were employed. The main physical processes in the ERB manifested more clearly in these distributions, and for protons with fd>0.5 mHz at L>3, their distributions in the {fd,L} space have a more regular shape than in the {E,L} space. It has also been found that the quantity of the ERB protons with fd ∼ 1–10 mHz at L∼2 does not decrease, as it does for protons with E > 10–20 MeV (with fd>10 mHz), but increases with an increase in solar activity. This means that the balance of radial transport and loss of ERB low-energy protons at L∼2 is disrupted in favor of transport of these protons: the effect of an increase in the radial diffusion rates with increasing solar activity overpowers the effect of an increase in the density of the dissipative medium.