Results from the SEP modelling. Top panels (a): 1 au cumulative proton crossing map for 3D test particle simulation of GLE 73. The location of the HCS is from the SDO/HMI model, and the injection region is centred at the flare location, W02 S26. (b): Crossing map with HCS removed. Observer footpoints are as follows: Earth (blue square), SolO (green square), Mars (brown square), Parker (purple square), STA (red square), Bepi (yellow square). Bottom panels: (c) Observations (black) with simulation results for no HCS (blue), 60 × 60° injection for the SDO/HMI HCS and 0.3 au mean free path (red), 60 × 60° injection for the SDO/HMI HCS and 0.1 au mean free path (cyan), and 60 × 60° injection with 0.3 au mean free path for the ADAPT HCS (yellow). Observers shown in Ci–iv are for GOES, Parker Solar Probe, STA, and SolO.