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  • Solar Energetic Proton Acce...
    Filwett, Rachael J.; Jaynes, Allison N.; Baker, Daniel N.; Kanekal, Shrikanth G.; Kress, Brian; Blake, J. Bern

    Journal of geophysical research. Space physics, June 2020, 2020-06-00, 20200601, Volume: 125, Issue: 6
    Journal Article

    In this study we examine the ability of protons of solar origin to access the near‐equatorial inner magnetosphere. Here we examine four distinct solar proton events from 20–200 MeV, concurrent with both quiet time and storm time conditions using proton data from the ACE satellite in the solar wind upstream of Earth and data from the Relativistic Electron Proton Telescope (REPT) instrument aboard Van Allen Probes. We examine the direct flux correspondence between interplanetary space and the inner magnetosphere. Small substructures in interplanetary space are observable in the REPT flux profiles, which can penetrate down to L values of ≤4. Furthermore, there are orbit‐to‐orbit variations in the west‐to‐east anisotropic flux ratios. The anisotropic flux ratios are used as a proxy for cutoff energies and display cutoff variations with L shell and energy. The dependence of the anisotropic flux ratio on Dst values is shown. The results paint a picture of highly dynamic spatial and temporal proton cutoff rigidities in the near‐equatorial inner magnetosphere. Key Points Small flux substructures in interplanetary space are observed in the inner magnetosphere West‐to‐east flux ratios are used as a proxy for cutoff location and energy West‐to‐east flux ratios are highly dynamic from orbit to orbit and respond quickly to magnetospheric changes