Influence of Electron-Impact Multiple Ionization on Equilibrium and Dynamic Charge State Distributions: A Case Study Using Iron

TL;DR

This study investigates how electron-impact multiple ionization (EIMI) affects charge state distributions in plasmas, revealing its significance in non-equilibrium conditions like impulsive heating, which impacts plasma modeling and spectroscopy.

Contribution

First to incorporate EIMI cross-sections into charge state distribution calculations for both equilibrium and non-equilibrium plasmas, highlighting its importance in dynamic conditions.

Findings

EIMI has minimal effect on equilibrium charge distributions.

EIMI significantly influences non-equilibrium plasmas with temperature oscillations.

Implications for modeling impulsively heated astrophysical plasmas like the solar corona.

Abstract

We describe the influence of electron-impact multiple ionization (EIMI) on the ionization balance of collisionally ionized plasmas. We are unaware of any previous ionization balance calculations that have included EIMI, which is usually assumed to be unimportant. Here, we incorporate EIMI cross-section data into calculations of both equilibrium and non-equilibrium charge-state distributions (CSDs). For equilibrium CSDs, we find that EIMI has only a small effect and can usually be ignored. However, for non-equilibrium plasmas the influence of EIMI can be important. In particular, we find that for plasmas in which the temperature oscillates there are significant differences in the CSD when including versus neglecting EIMI. These results have implications for modeling and spectroscopy of impulsively heated plasmas, such as nanoflare heating of the solar corona.