Ion Charge States in Halo CMEs: What can we Learn about the Explosion?

TL;DR

This paper introduces a new modeling approach to analyze ion charge states in halo CMEs, linking in situ ACE data with CME evolution models to infer plasma heating and ionization processes.

Contribution

The study develops a quantitative model integrating CME hydrodynamics and ionization equations, enhancing understanding of plasma heating and charge state distributions in CMEs.

Findings

Plasma in CME core often requires additional heating after eruption.

CME cavity plasma typically does not undergo further ionization.

Model limitations stem from uncertainties in CME evolution modeling.

Abstract

We describe a new modeling approach to develop a more quantitative understanding of the charge state distributions of the ions of various elements detected in situ during halo Coronal Mass Ejection (CME) events by the Advanced Composition Explorer (ACE) satellite. Using a model CME hydrodynamic evolution based on observations of CMEs propagating in the plane of the sky and on theoretical models, we integrate time dependent equations for the ionization balance of various elements to compare with ACE data. We find that plasma in the CME ``core'' typically requires further heating following filament eruption, with thermal energy input similar to the kinetic energy input. This extra heating is presumably the result of post eruptive reconnection. Plasma corresponding to the CME ``cavity'' is usually not further ionized, since whether heated or not, the low density gives freeze-in close the the Sun. The current analysis is limited by ambiguities in the underlying model CME evolution. Such methods are likely to reach their full potential when applied to data to be acquired by STEREO when at optimum separation. CME evolution observed with one spacecraft may be used to interpret CME charge states detected by the other.