3D Nonequilibrium Ionization and Spectroscopic Modeling of Coronal Mass Ejections. III. Charge State Evolution

The ionization state of plasmas leaving the Sun freezes in low in the solar corona and carries information about the inner corona through the heliosphere. In situ charge state measurements provide excellent diagnostic tools for studying the early evolution and energetics of the solar wind and coronal mass ejections (CMEs). Three-dimensional global magnetohydrodynamics models allow us to link the measured in situ charge states to the heating/cooling mechanisms in the low corona to understand its evolution. In this final paper of the series, we use the 2008 April 9 CME (the “Cartwheel CME”) simulated with the Alfvén Wave Solar atmosphere Model to understand the evolution of the charge states. The highest-ionization material in the flux rope is caused by the high temperatures early in the eruption, which freezes in quickly due to the large adiabatic expansion rates. The prominence preserves low ionization state material to 1 au because of the high radiative cooling rates, but only occupies about 10% of the cross-sectional area of the CME, making it less likely to be observed in situ. We discuss in situ charge state distribution properties that can be used for understanding CME plasmas and their heating processes. We show that between the Extreme ultraviolet Imaging Spectrometer slit location (1.1 R _⊙) and the freeze-in height, there is a significant amount of unobserved charge state evolution that would be lost without the use of models.