Multi-population model for Iron ions in ICMEs

If a CME is detected in-situ by a spacecraft located in the interplanetary medium, it is then called an Interplanetary Coronal Mass Ejection (ICME). Charge states of heavy ions reflect important information about the coronal temperature profile due to the freeze-in effect and it is estimated that Iron ions freeze in at the heights of ~5 solar radii.

To identify different populations of Iron charge state composition of ICMEs and determine their sources,we developed a model which independently uses two, three, and four populations of Iron ions to fit the measured charge state distribution in ICMEs detected by the Advanced Composition Explorer (ACE) at 1AU. Three parameters are used to identify a certain population, i.e., freeze-in temperature, relative abundance and kappa value which together describe the potential non-Maxwellian kappa-distributions of coronal electrons.