Solar wind and IMF conditions around the 2022 December 24 ³He-rich SEP event. (a) Local IMF for 11 days surrounding the event. The shaded interval marks the ICME passage. (b)–(i) Three days of measurements within the ICME. (b) SIS C–Fe inverse-ion-speed spectrogram. The SEP event start and stop are marked by the vertical green lines, and the SEP dropouts are indicated by the orange shaded regions. (c) SIS He mass spectrogram at 0.4–10 MeV nucleon⁻¹. (d)–(f) SWA-PAS solar wind proton moments. The large variability during the SEP event likely reflects the the very low proton densities. (g) Solar wind energy spectrogram. Possible He⁺ enhancement is indicated by the blue shaded region. (h) IMF components and magnitude. (i) SWA-EAS 91 eV suprathermal electron PADs. Dashed black lines mark intervals of electron depletion during the later dropout sequence.