Irregular Proton Injection to High Energies at Interplanetary Shocks - Trotta, D; Horbury, TS; Lario, D; Vainio, R; Dresing, N; Dimmock, A; Giacalone, J; Hietala, H; Wimmer-Schweingruber, RF; Berger, L; Yang, L (The Astrophysical Journal Letters, 2023)