Investigation of solar proton access into the inner magnetosphere on 11 September 2017

The maximum and minimum cutoff rigidity at each point along the orbit of Van Allen Probe A is numerically computed by extending the code to calculate cutoff rigidity for particles coming from arbitrary direction.

Pulse height analyzed (PHA) data have the advantage of providing individual particle energies and effectively excluding background high-energy proton contamination. This technique is adopted to study the cutoff locations for solar protons with different energy. The results demonstrate that cutoff latitude is lower for solar protons with higher energy, consistent with low-altitude vertical cutoffs.