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The Evolution of Ion Charge States in Coronal Mass Ejections

Presentation #402.05 in the session Particle Interactions Throughout the Heliosphere.

Published onSep 18, 2023
The Evolution of Ion Charge States in Coronal Mass Ejections

We model the observed charge states of the elements C, O, Mg, Si, and Fe in the coronal mass ejections (CMEs) ejecta. We concentrate on “halo” CMEs observed in situ by ACE/SWICS to measure ion charge states, and also remotely by STEREO when in near quadrature with Earth, so that the CME expansion can be accurately specified. Within this observed expansion, we integrate equations for the CME ejecta ionization balance, including electron heating parameterized as a fraction of the kinetic and gravitational energy gain of the CME. We also include the effects of non-Maxwellian electron distributions, characterized as a kappa function. Focusing first on the 2010 April 3 CME, we find a significantly better match to observed charge states with kappa close to the theoretical minimum value of kappa = 3/2, implying a hard spectrum of non-thermal electrons. Similar results come from the 2011 February 15 event, although it is quite different in terms of its evolution. We discuss the implications of these values, and of the heating required, in terms of the magnetic reconnection Lundquist number and anomalous resistivity associated with CME evolution close to the Sun.

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