On the Possible Mechanisms of the SEP Event and Electron Enhancement over the SEP Decay Phase on 2023 August 5

Abstract We carry out this study on the solar energetic particle (SEP) event that occurred on 2023 August 5 over the ascending phase of the current solar cycle 25. It is found that the SEP event might have been initiated by the M1.6 flare, while the SEP peak was caused by the coronal shock manifested in DH -type II radio burst over the propagation phase of a halo coronal mass ejection (CME; ∼1000 km s −1 ), thus creating a mixed SEP event. There were two enhancements of the electron fluxes lying over the SEP rise and decay phase. It is surprising that, despite a stronger flare (X1.6) and a faster halo CME (∼1647 km s −1 ), there was no SEP enhancement during the second enhancement of the electron fluxes. In order to investigate this, we make an additional effort to analyze the X1.6 flare based on the availability of the temporal, spectral, and spatial evolution of the electromagnetic radiation components. It is observed that the CME shock was aligned with the flare eruption direction and was close to the western limb (W77°), and thus the radially moving CME shock missed the Earth. In another development, it is observed that the electron impulsive phase lies over the type III radio bursts, indicating that the electrons might have escaped directly during the eruption. The radio flux and radio dynamic spectra of a higher frequency lie over the rise phase of the soft X-ray derivative, indicating that a large number of electrons travelled through magnetic fields.