Catalogue and statistics of > 100 MeV solar proton events during solar cycles 23–25 from SOHO/ERNE observations

Context. The SPEARHEAD (specification, analysis, and re-calibration of high-energy particle data) project, funded by the European Union’s Horizon Europe programme, enhances the accuracy and usability of high-energy particle measurements. It investigates particle acceleration, release, and transport during solar eruptions by refining instrument response functions and cross-calibrating datasets. This effort supports in-depth analyses of solar energetic particle (SEP) events and provides public data products.

Aims. We present a comprehensive catalogue of > 100 MeV proton events identified from May 1996 to August 2024 using SOHO/ERNE penetrating-particle rates, together with associated solar phenomena derived from multi-instrument observations.

Methods. The SEP events were detected through a systematic scan of ERNE/HED counter data and cross-calibrated with SOHO/EPHIN to derive peak fluxes and fluences. Each event was associated with its likely parent eruption using X-ray (XR) (GOES/XRS, RHESSI, SolO/STIX), radio (Wind/WAVES, STEREO/WAVES, ground-based observatories), and γ-ray (Fermi/LAT) observations, CMEs (SOHO/LASCO), and ground-level enhancements (GLEs) (neutron monitors). Timings and physical properties were systematically compared to investigate the relationships between SEP onset, flare evolution, CME kinematics, and radio signatures.

Results. Associations were established for 96% of CMEs and 76% of X-ray flares; all events exhibited type III radio bursts, while 95% had type II, and 53% type IV. > 100 MeV γ-rays were identified in 65 events, and 22 were linked to GLEs or sub-GLEs. Statistical analyses reveal that most SEP releases closely follow flare and CME onsets, with moderate SEP-XR-CME correlations, and a strong SEP-GLE fluence link. These results indicate that high-energy SEP events are typically associated with strong solar activity signatures, with the observed intensities and timings strongly modulated by magnetic connectivity and coronal conditions.

Conclusions. This catalogue provides the most extensive reference to date for high-energy SEP events over solar cycles 23–25, establishing a unified framework for future investigations of extreme particle acceleration.