Authors: Abdullah A. Shmies (The University of Texas at San Antonio), Maher A. Dayeh (Southwest Research Institute), Radoslav Bucik (Southwest Research Institute), Samuel T. Hart (The University of Texas at San Antonio)

The exact origins and acceleration mechanisms governing solar energetic particle (SEP) events remain an open question in heliophysics. SEP production is thought to be dominated by two main mechanisms: (i) flare-associated acceleration via magnetic reconnection processes and (ii) shock-accelerated processes in association with fast coronal mass ejections (CMEs). In extreme cases, SEP events can produce a significant increase in the number of high-energy particles (10s – 100s of MeV), posing significant radiation threats to space assets. Because these extreme events are associated with bright (M- & X-class) solar flares and high-speed CMEs, the production of high-energy particles likely arises from the interplay between flare and shock-accelerated processes. Understanding the role each source plays in SEP production can significantly improve our predictive capabilities to mitigate the effects of space weather.

In this study, we perform statistical analysis on a large set of extreme SEP events listed in NOAA’s GOES list. The list comprises 130 SEP events including 18 Ground Level Events (GLEs) and 4 sub-GLEs recorded between 1997 and 2017. Among these, we identify SEP events with available high-energy fluxes suitable for timing analysis. Using a velocity dispersion analysis approach, we determine each event’s solar particle release (SPR) time and compare it to the onset of the parent X-ray flare. By correlating the time difference between the flare and particle release with the spectral properties and abundance ratios of both protons and heavy ions, we assess the contribution of flares to the production of SEPs in these extreme events.