Authors: Alyssa Russell (University of Michigan), Liang Zhao (University of Michigan), Jim Raines (University of Michigan)

Suprathermal heavy ions, the heavy ions with a higher kinetic energy than their thermal counterparts, make up a small fraction of the solar wind composition. Recent studies on the WIND/STICS observations show that these ions (such as O6+) become more abundant during fast solar wind and interplanetary coronal mass ejection (ICMEs) events, which make the abundance of suprathermal heavy ion O6+ a useful diagnostic tool for solar wind events and essential to our knowledge of suprathermal heavy ions and solar wind as a whole. In this work, we analyze the heavy ion composition data from the SupraThermal Ion Composition Sensor (STICS) onboard the Wind spacecraft over 1998 to 2018. We visually found the dependence of the O6+ phase space density on the energy per charge (E/q) ratio has a unique behavior, and began investigating the event properties to identify additional events. We investigate the phase space density and the daily averaged O6+ counts over each E/q and determine their peaks and spreads of the E/q over each event. We find that O6+ events have a daily average of over 100 counts, a normalized peak of over 20 counts, and a full-width-half-maximum of less than 10 E/q. Through these analyses, we find 42 O6+ events from 455 ICME and shock time periods and identify two types of events. The first type of event, tapering events, is such that the O6+ is distributed rather hot (in high E/q bins) in the ICME sheath then sharply cools (in low E/q bins) immediately following the end of the ICME event. The second type of event, beam events, is such that the O6+ begins as a cool beam (in low E/q bins) and remains as such throughout the event. We then studied the association of these events with ICMEs, shocks, and the solar cycle. We find that the tapering events were highly associated with ICMEs while beam events varied more, occurring up to 3 days after an ICME and shock event. Both types of events are unexpected and may hold the key to explain the source and acceleration process of O6+ in fast solar wind and ICMEs.