Multi-spacecraft Observations of the Evolution of Interplanetary Coronal Mass Ejections between 0.3 and 2.2 au: Conjunctions with the Juno Spacecraft

Abstract

We present a catalog of 35 interplanetary coronal mass ejections (ICMEs) observed by the Juno spacecraft and at least one other spacecraft during its cruise phase to Jupiter. We identify events observed by MESSENGER, Venus Express, Wind, and STEREO with magnetic features that can be matched unambiguously with those observed by Juno. A multi-spacecraft study of ICME properties between 0.3 and 2.2 au is conducted: we first investigate the global expansion by tracking the variation in magnetic field strength with increasing heliocentric distance of individual ICME events, finding significant variability in magnetic field relationships for individual events in comparison with statistical trends. With the availability of plasma data at 1 au, the local expansion at 1 au can be compared with global expansion rates between 1 au and Juno. Despite following expected trends, the local and global expansion rates are only weakly correlated. Finally, for those events with clearly identifiable magnetic flux ropes, we investigate the orientation of the flux rope axis as they propagate; we find that 64% of events displayed a decrease in inclination with increasing heliocentric distance, and 40% of events undergo a significant change in orientation as they propagate toward Juno. The multi-spacecraft catalog produced in this study provides a valuable link between ICME observations in the inner heliosphere and beyond 1 au, thereby improving our understanding of ICME evolution.