COMPOSITION STRUCTURE OF INTERPLANETARY CORONAL MASS EJECTIONS FROM MULTISPACECRAFT OBSERVATIONS, MODELING, AND COMPARISON WITH NUMERICAL SIMULATIONS

We present an analysis of the ionic composition of iron for two interplanetary coronal mass ejections (ICMEs) observed on 2007 May 21-23 by the ACE and STEREO spacecraft in the context of the magnetic structure of the ejecta flux rope, sheath region, and surrounding solar wind flow. This analysis is made possible due to recent advances in multispacecraft data interpolation, reconstruction, and visualization as well as results from recent modeling of ionic charge states in MHD simulations of magnetic breakout and flux cancellation coronal mass ejection (CME) initiation. We use these advances to interpret specific features of the ICME plasma composition resulting from the magnetic topology and evolution of the CME. We find that, in both the data and our MHD simulations, the flux ropes centers are relatively cool, while charge state enhancements surround and trail the flux ropes. The magnetic orientations of the ICMEs are suggestive of magnetic breakout-like reconnection during the eruption process, which could explain the spatial location of the observed iron enhancements just outside the traditional flux rope magnetic signatures and between the two ICMEs. Detailed comparisons between the simulations and data were more complicated, but a sharp increase in high iron charge states in the ACE and STEREO-A data during the second flux rope corresponds well to similar features in the flux cancellation results. We discuss the prospects of this integrated in situ data analysis and modeling approach to advancing our understanding of the unified CME-to-ICME evolution.