Ground-Level Enhancement of 8 June 2024 (GLE 75) Caused by Solar Energetic Particles

Abstract

Solar eruptive events such as flares and coronal mass ejections can accelerate charged particles up to nearly relativistic energies producing so-called solar energetic particles (SEPs). Some of those SEPs can propagate towards Earth and be registered by, e.g., particle detectors onboard satellites. Favourable acceleration conditions make strong SEP events possible with a high flux of high-energy (> 500 MeV) protons, which can be registered even on the ground by neutron monitors (NMs) as rapid enhancements of their count rate over the background. Such events are accordingly called ground-level enhancements (GLEs). GLEs are rare, with only 73 events registered from 1942 to 2023, and three more GLEs 74 – 76 occurred in 2024, close to the maximum of solar activity. In this work, we report GLE 75 that happened on 8 June 2024, initially missed during real-time monitoring, but identified retrospectively. The SEP event, which induced the GLE, was associated with a flare from the solar active region 13697 (13664 on the previous solar rotation). It caused statistically significant increases in the count rate of NMs Dome C, South Pole, and Peawanuck, as well as in the proton intensity measured by Geostationary Operational Environmental Satellite GOES-16. Here, we show the GLE in NM data, describe the procedure of evaluation of its statistical significance, and present the analysis with reconstruction of the spectral and angular SEP distributions.