The role of geomagnetic storm-induced energetic particle precipitations in the modification of the ionosphere over the American and African longitudinal sectors

Geomagnetic storms are associated with changes in electron and proton fluxes in the radiation belts, leading to precipitation. However, most past studies have been done based on storms’ intensities. This study investigates the roles of eight geomagnetic storms, classified by their intensities using Dst threshold conditions, and interplanetary drivers, in the production of Energetic Particle Precipitation (EPP), and their subsequent modification of ionospheric irregularities and Total Electron Content (TEC). We used energetic particle fluxes, TEC, interplanetary magnetic field, and solar wind data. The rate of TEC index (ROTI) was used as a proxy for ionospheric irregularities. In this study, the ability of a storm to induce EPPs is predominant and significant during the recovery phases of storms. Consequently, the modifications of the ionosphere caused by EPPs were mostly pronounced during the recovery phase of a storm. At the recovery phases, enhanced EPPs induced by intense sheath (SH)- and Corotating Interaction Region (CIR)-driven storms caused corresponding enhancements in TEC and ionospheric irregularities, while that of intense magnetic cloud (MC)-driven storm showed no significant effect on TEC and irregularities. Furthermore, enhanced EPP induced by intense and moderate MC + SH-driven storms caused little or no change in TEC and ionospheric irregularities. In addition, an enhanced EPP induced by moderate sheath- and MC-driven storms caused depletion in TEC and irregularities. Irregularities were more prevalent at the low- and high-latitude, but less in occurrences at the mid-latitude in the African sector. Overall, from this study, the African sector responded more to the energetic particles than the American sector. Irregularities at the high-latitude stations were generally high and frequent regardless of the phase, magnitude, driver, or local times of occurrence of storms. The storm-induced EPP enhancements were more significant in the southern hemisphere than in the northern hemisphere, and the events of the equinoctial months showed more dependence on EPPs.