Energetic, relativistic, and ultrarelativistic electrons: Comparison of long-term VERB code simulations with Van Allen Probes measurements

• Published in: Journal of geophysical research. Space physics 2015-05, Vol.120 (5), p.3574-3587
• Main Authors: Drozdov, A. Y., Shprits, Y. Y., Orlova, K. G., Kellerman, A. C., Subbotin, D. A., Baker, D. N., Spence, H. E., Reeves, G. D.
• Format: Article
• Language: English
• Subjects: Astrophysics; Computer simulation; Cyclotrons; Diffusion; Electrons; EMIC waves; Geophysics; long-term simulation; Magnetic fields; Pitch angle; Probes; Scattering; Simulation; Space probes; Spectrometers; VERB code
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1002/2014JA020637

In this study, we compare long‐term simulations performed by the Versatile Electron Radiation Belt (VERB) code with observations from the Magnetic Electron Ion Spectrometer and Relativistic Electron‐Proton Telescope instruments on the Van Allen Probes satellites. 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 ultrarelativistic (>2 MeV) electrons. One year of relativistic electron measurements (μ = 700 MeV/G) from 1 October 2012 to 1 October 2013 are well reproduced by the simulation during varying levels of geomagnetic activity. However, for ultrarelativistic energies (μ = 3500 MeV/G), the VERB code simulation overestimates electron fluxes and phase space density. These results indicate that an additional loss mechanism is operational and efficient for these high energies. The most likely mechanism for explaining the observed loss at ultrarelativistic energies is scattering by the electromagnetic ion cyclotron waves. Key Points VERB code reproduces the dynamics of relativistic multi‐MeV electrons Whistler waves and radial diffusion cannot explain their observed losses Scattering by EMIC waves is the most likely explanation for the observed losses