Ground-Level Enhancements (GLEs) are rare solar energetic particle (SEP) events in which ions are accelerated to relativistic energies, generating secondary particles in Earth’s atmosphere that produce detectable increases in ground-based neutron-monitor signals above the galactic cosmic-ray background. Despite their significant space-weather impact, the pre-eruptive conditions and particle acceleration mechanisms responsible for GLEs remain poorly understood.

Using GOES soft X-ray observations in the 1–8 Å and 0.5–4 Å channels, we derive peak temperatures and emission measures for flares associated with 180 major SEP events, including 24 GLEs, following Ryan et al. (2012). We examine how these thermal properties relate to SEP peak flux and fluence across multiple particle energies.

We find that GLE-associated flares are, on average, hotter and exhibit higher peak emission measures than non-GLE-associated flares, although there is partial overlap between the two populations. Correlations between flare temperature and SEP intensity (peak flux and fluence) increase with particle energy. We conclude that high-energy SEP populations tend to be associated with hotter solar flares.