Investigation of Solar Proton Access into the Inner Magnetosphere on 11 September 2017

Solar energetic protons are shielded by the Earth's magnetosphere and are known to exhibit an east-west asymmetry effect. Solar protons access to the inner magnetosphere at low latitude and the cutoff energies for protons arriving from different directions at different altitudes over the inner magnetosphere remain unquantified. In this study, solar protons access to the inner magnetosphere on 11 September 2017 is quantitatively examined using a Tsyganeko plus IGRF magnetic field model. The measured proton flux is shown to depend largely on particle arrival direction. The maximum and minimum cutoff rigidities along the Van Allen Probe orbit are numerically computed by extending the CISM-Dartmouth geomagnetic cutoff code [Kress et al., 2010] for arbitrary direction. Direct comparison will be made between the modeled flux and Van Allen Probe observation.