Authors: Yeimy Rivera (CfA|Harvard & Smithsonian), John C. Raymond (CfA|Harvard & Smithsonian), Enrico Landi (UMich), Susan T. Lepri (UMich), Ben Alterman (UMich), Kathy Reeves (CfA|Harvard & Smithsonian), Mike Stevens (CfA|Harvard & Smithsonian)

The elemental composition measured in the solar wind is a direct reflection of the fractionation processes at its source region. The variation in elemental composition of coronal structures and their associated solar wind streams is largely attributed to fractionation based on the First Ionization Potential (FIP) effect. However it is unclear to what degree gravitational settling plays a role in the plasma’s chemical makeup. Studies of interplanetary coronal mass ejections (ICMEs) measured in the heliosphere often show large variation in the elemental composition across the CME body and throughout the solar cycle. Nevertheless, it is not always clear what processes drive the changes observed. To gain insight to this variation, we have quantified the impact of gravitational settling in the ejecta, along with the FIP effect, to examine its influence on the compositional variation observed in ICMEs. We find that the ejecta exhibits some gravitational settling effects in approximately 33% of all ICME periods across solar cycle 23. We also find gravitational settling appears to be most prominent in ICMEs during solar minimum. In ongoing work, we also examine the pre-eruptive CME source region at the Sun to further investigate the impact of gravitational settling in the plasma composition.