Collection, Collation, and Comparison of Near‐Earth In Situ CME Boundaries

Abstract Coronal mass ejections (CMEs) drive space weather throughout the heliosphere so knowledge of their internal properties is key to understanding and eventually forecasting their effects. Typically observations are limited to single‐spacecraft encounters sampling one path that may or may not be representative of the overall structure. Many catalogs exist listing the observed boundaries of a CME ejecta and any CME‐driven sheath. Often there are large differences in the reported boundaries across different catalogs. We introduce the Living List of Attributes Measured in Any In situ CME Encounter (LLAMAICE), which collects and collates existing near‐Earth catalogs into a new meta‐catalog. We have added a new set of boundaries, building upon the existing information that includes additional mixed regions containing mixed signatures of the pristine sheath and ejecta core (EC). This first version of LLAMAICE covers February 1995 to December 2006, corresponding to 1,516 entries for 396 unique CMEs. We use LLAMAICE to quantify the variation in mean sheath/ejecta properties from using boundaries from different catalogs and/or data from using ACE versus Wind data. We also reconstruct flux rope (FR) orientation for each set of bounds/spacecraft, which are well‐known to be quite sensitive. For both studies, the cross‐catalog variations exceed the cross‐spacecraft variations. The reconstructed FR handedness agrees 77% of the time between spacecraft but only 47% across catalogs. The orientations vary between spacecraft by 2.2/3.4 in inclination/longitude but 4/10 times that between catalogs.