Investigation of Solar Proton Access into the inner magnetosphere on 11 September 2017

TitleInvestigation of Solar Proton Access into the inner magnetosphere on 11 September 2017
Publication TypeJournal Article
Year of Publication2019
AuthorsQin, M, Hudson, M, Kress, B, Selesnick, R, Engel, M, Li, Z, Shen, X
JournalJournal of Geophysical Research: Space Physics
Date Published04/2019
Keywordscutoff energy; cutoff location; Dartmouth geomagnetic cutoff code; Pulse height analyzed data; Solar proton; straggling function; Van Allen Probes
AbstractIn this study, access of solar energetic protons to the inner magnetosphere on 11 September 2017 is investigated by computing the reverse particle trajectories with the Dartmouth geomagnetic cutoff code [Kress et al., 2010]. 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‚Äźheight analyzed (PHA) data has 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. Both the observations and numerical results show that proton access into the inner magnetosphere depends strongly on angle between particle arrival direction and magnetic west. The numerical result is approximately consistent with the observation that the energy of almost all solar protons stays above the minimum cutoff rigidity.
Short TitleJ. Geophys. Res. Space Physics

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