ИСТИНА

In this study, we compare long-term simulations performed by the Versatile Electron Radiation Belt (VERB) code with observations from the MagEIS and REPT instruments on the Van Allen Probes. The model takes into account radial, energy, pitch-angle and mixed diffusion, losses into the atmosphere, and magnetopause shadowing. We consider the energetic (>100 KeV), relativistic (~0.5-1 MeV) and ultra-relativistic (>2 MeV) electrons. One year of relativistic electron measurements (μ=700 MeV/G) from October 1, 2012 to October 1, 2013 are well reproduced by the simulation during a period of the various geomagnetic activity. However, for ultra-relativistic energies (μ=3500 MeV/G), the VERB code simulation overestimates electron phase space density (PSD). These results indicate that an additional loss mechanism is operational and efficient for these high energies. We discuss possible solutions for improving the modeling of the radiation belts dynamics.