Empirical model of pitch-angle distributions of trapped protons on the inner boundary of the Earth’s radiation belt

We have made a generalization of experimental data on the fluxes of trapped protons that were detected by various instruments on three low-orbit satellites ( NOAA-17, Universitetskii-Tatiana , and CORONAS-F ) during April of 2005. Based on these data, a new quantitative model is suggested to describe the fluxes of trapped protons. It allows one, using analytical expressions, to predict the fluxes of protons with energy from 30 keV to 140 MeV under quiet geomagnetic conditions in the period close to the solar activity minimum at drift shells L = 1.14–1.4. The suggested model establishes differential directional fluxes of protons as a function of pitchangle on the geomagnetic equator and takes into account the anisotropy of trapped particles on the lower boundary of the Earth’s radiation belt.