Solar Energetic Protons in the Interplanetary Medium and in Near-Earth Space on May 8–11, 2024

We analyze the dynamics of solar energetic particles during the extreme solar activity interval of May 8–11, 2024, when a large number of M- and X-ray flares accompanied by several halo-type coronal mass ejections (CMEs) were observed on the Sun in the active region 13664. The propagation of solar protons occurred against the background of a strongly disturbed interplanetary medium. A comparison the time profile of particle fluxes measured at the Earth’s orbit and in the vicinity of the L1 libration point made it possible to identify some characteristic features associated with the generation of particles near the Sun and with the modulation of particle fluxes by solar wind structures. The paper discusses a slow increase in proton fluxes during the interval of May 8–10, which can be associated with three stages of acceleration: (1) on the shock wave in front of a CME; (2) during the approach of the fast CME to the slow one; and (3) on the shock wave propagating inside the interplanetary CME. The influence of shock waves observed near the Earth on proton fluxes on May 10 is shown. It is found that accelerated protons can accumulate inside magnetic clouds of interplanetary CME. We also studied a solar proton event (SPE) of May 11, 2024, when an SPE ground level enhancement was observed—GLE 74, which was caused by protons with E > 1 GeV. It is shown that a dispersionless enhancement at the beginning of the SPE can be explained by the modulation of proton fluxes by a tube-type structure bounded by two magnetic clouds and connected to the acceleration region on the Sun.