Analysis of solar energetic particle (SEP) event on the geomagnetic environment during 24th solar cycle

Abstract We report a study of major solar energetic particle (SEP) and ground level enhancement (GLE) events that occurred during the first 62 months of the rising phase of 24th solar cycle. Our objective is to comprehend the key factors that influence the severity and occurrence of such events. Coronal mass ejection (CME) speed (serves as or is) a reliable indicator of SEP and GLE events, as it consistently supports the shock acceleration mechanism. Some very fast CMEs, which likely have accelerated particles upto GeV energies, they may not result in a GLE event due to poor latitudinal connectivity. We have emphasized that the CME speed, magnetic connectivity to Earth, and ambient conditions as the main or primary factors that contribute to the lack of high-energy particle events during cycle 24. Furthermore, we observed that even well-connected fast CMEs that did not seem to have accelerated high-energy particles due to potentially unfavorable prevailing conditions such as high Alfven speed and overall reduction in acceleration efficiency in cycle 24. These conclusions are generally supported by insights gleaned from the observation of the time series of SW-IMF parameters on the flare day.