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

The heavy ion composition is a crucial diagnostic to determine the coronal source region properties and acceleration processes of coronal mass ejection events and solar wind. The charge states of these ions are frozen-in at the corona, therefore recording the thermal properties of electron temperature and density of the plasma in the coronal origins. The sun produces large expulsions of plasma and energy from the solar corona called interplanetary coronal mass ejections (ICMEs) that carry a unique distribution of heavy ions in comparison to regular solar wind signatures. Suprathermal heavy ions are the heavy ions with a higher kinetic energy than their thermal counterparts that become more abundant during ICMEs and fast solar wind. A comprehensive study of suprathermal heavy ion composition can improve our understanding of solar wind events as they are key components in questions such as whether they are the seed population of even higher energy ions and whether they can be used as ICME predictors. In this study, we characterize the suprathermal heavy ions throughout the mission lifetime of the Wind spacecraft. We analyze the species densities of O7+, O6+, C6+, and C5+, and charge state ratios of O7+/O6+  and C6+/C5+ in the thermal and suprathermal ranges during ICME events and fast solar wind time periods. The carbon ratios were similar across the suprathermal and thermal ranges, but the oxygen ratios were larger in both the ICME and non-ICME events. This is due to differences in the suprathermal and thermal O6+ in ICMEs, and O6+ and O7+ in non-ICMEs. The suprathermal heavy ions therefore provide different information to the thermal ions which may be due to acceleration processes, source regions, or other factors. The lack of depletion of suprathermal O7+/O6+, particularly in the non-ICME, generally fast wind events, implies that the suprathermal fast wind population may not originate in coronal holes like the thermal fast wind, or that their ratios are developed further out in the heliosphere rather than the corona. This study provides the first steps toward a full characterization of the suprathermal heavy ions and the important information they provide.