Tuesday

3D test particle simulations of historic Ground Level Enhancement (GLE) events are performed to investigate the propagation and spatial distribution of relativistic solar protons within the heliosphere. Multiple past GLEs are considered that possess a variety of properties of the associated solar events, e.g. a range of source flare longitudes and coronal mass ejection velocities. The test particle model, which includes drift effects, is used to explore the influence a heliospheric current sheet (HCS) has on the propagation of protons. For example, historic GLEs with a source location close to and far from the HCS, as well as poorly and well-connected events with respect to Earth are considered. The modelling is performed for high energy (300-1200 MeV) protons to represent the energetic conditions under which these GLEs occur. The derived intensity profiles at 1AU are compared to observations from HEPAD onboard GOES and neutron monitor data. The historic events are simulated both with and without a current sheet to see the effect on the intensity profile at Earth's location. Overall, the HCS is found to make a difference in 75% of the simulated GLE events.