Ground level enhancement events of Solar cycle 23

Abstract

Ground level enhancement (GLE) events, typically in the GeV energy range, are the most energetic of solar energetic particle (SEP) events with the protons penetrating Earth’s neutral atmosphere. During solar cycle 23, sixteen GLE events were observed with excellent data coverage of associated solar eruptions. The source of these GLE particles has been examined in this paper using white light observations of coronal mass ejections, type II radio bursts, and soft X-ray flares. It has been shown that the GLE events are consistent with shock acceleration in every single case. While the possibility of the presence of a flare component during GLE events cannot be ruled out, it can be definitely said that a shock component is present in all the GLE events. During 18 April 2001 GLE event, the source was located ~30 degrees behind the west limb, which is too far away from the magnetic field lines connecting Earth and hence the flare component can be ruled out. Also the presence of interplanetary shocks associated with the GLEs is shown using radio and <i style="">in-situ</i> observations.