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

Abstract

<p><em>Context.</em> 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.</p><p><em>Aims.</em> 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.</p><p><em>Methods.</em> 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 <em>γ</em>-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.</p><p><em>Results.</em> 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 <em>γ</em>-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.</p><p><em>Conclusions.</em> 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.</p>