Statistical Study and Live Catalog of Multispacecraft 3He-rich Time Periods over Solar Cycles 23, 24, and 25

Using ion measurements from Ultra-Low-Energy Isotope Spectrometer observations on board Advanced Composition Explorer and Solar Isotope Spectrometer observations on board the Solar Terrestrial Observatory (STEREO)-A and STEREO-B spacecraft, we have identified 854 3He-rich time periods between 1997 September and 2021 March. We include all event types with observed 3He enhancements such as corotating interaction regions, gradual solar energetic particle (SEP) events, interplanetary shocks, and impulsive SEP events. We employ two different mass separation techniques to obtain 3He, 4He, Fe, and O fluences for each event, and we determine the 3He/4He and Fe/O abundance ratios between 0.32–0.45 and 0.64–1.28 MeV nucleon−1. We find a clear correlation in the 3He/4He and Fe/O abundance ratios between both energy ranges. We find two distinct trends in the 3He/4He versus Fe/O relation. For low 3He/4He values, there is a positive linear correlation between 3He/4He and Fe/O. However, at 3He/4He ∼ 0.3, Fe/O appears to reach a limit and the correlation weakens significantly. We provide a live catalog of 3He-rich time periods that includes the robust determination of the onset and end times of the 3He enhancements in SEP-associated periods for different types of events observed by multiple spacecraft. This catalog is available for public use. New releases will follow after major additions such as adding new periods from new missions (e.g., Parker Solar Probe and Solar Orbiter), identifying event types (impulsive SEP events, etc.), or adding new parameters such as remote observations detailing characteristics of the events’ active regions.