Exploring SEP Transport in Widespread Events with Different Heliospheric Current Sheet Models

Abstract

Understanding solar energetic particle transport in wide-longitude events remains a significant question in heliophysics. By utilizing the increasing number of available observers at various heliographic distances and longitudes, such as Parker Solar Probe and Solar Orbiter, we are able to further our understanding of these widespread events. This study presents 3D test particle modeling of three widespread events during the Parker era, each detected by at least four observers. The role of the heliospheric current sheet (HCS) in transporting particles to the wide longitudes observed in these events is evaluated. A newly updated and more sophisticated HCS model is used, incorporating three different configurations derived from the Wilcox Solar Observatory, Air Force Data Assimilative Photospheric Flux Transport, and Solar Dynamics Observatory/Helioseismic and Magnetic Imager (HMI) data (via Predictive Science, PSI) for each event. The modeled proton flux profiles at each observer location are compared against energetic proton measurements for each HCS configuration. We find that inclusion of the HCS is essential to reproduce both the wide longitudinal spread of particles and the observed flux profiles in all three events. For events with longitudinal separations exceeding 100°, the most intense fluxes, both observed and modeled, are associated with observers located nearest to the HCS. This is observed for the 2023 March 13 event, where two observers were located closer in longitude and radial distance than other observers to the source region, yet observed no solar energetic particle signatures due to their lack of proximity to the HCS. Among the three configurations, the HMI-PSI-derived HCS consistently yields the best agreement between observed and modeled flux profiles.