Authors: Amelia Lee (Mount Holyoke College), Rachael Filwett (Montana State University), Maher Dayeh (Southwest Research Institute), Robert Allen (Southwest Research Institute), Gang Li ( General Linear Space Plasma Lab)

Understanding why some impulsive SEP events are not constrained to a small longitudinal spread or undergo a large cross-field diffusion helps to increase our understanding of energetic particle transport and interplanetary magnetic field configuration. Impulsive SEP events last a few minutes to a few hours and have heightened 3He/4He and Fe/O ratios compared to solar wind abundances. Typically, these events have a longitudinal spread of 20°- 60°. However, for unknown reasons, some impulsive events have been observed to have a wide ( 130°) longitudinal spread (Wiedenbeck et al., 2012). In this study time-intensity profiles and energetic ion spectra for Helium (Helium-3 and Helium-4 when available), Carbon, Oxygen, and Iron in energy ranges from a few keV to 70 MeV are used to examine the longitudinal spread of six SEP events.

These events are April 2-3, 2019, April 4, 2019, April 20-23, 2019, July 11, 2020, July 20, 2020, and May 24-25, 2021, which were previously identified in McComas et al., 2019, Mitchell et al., (2023), Weidenbeck et al., 2020, or Mason et al., (2020). The analysis used four different spacecraft: Parker Solar Probe/IS⊙IS/EPI-Lo, ACE/ULEIS, STEREO-A/IMPACT/LET, and Solar Orbiter/EPD/SIS. We use the findings to discuss the longitudinal spread of heavy ion spectra which show a range of longitudinal spreads from event to event.