A new approach to analyzing solar coronal spectra and updated collisional ionization equilibrium calculations. II. Additional ionization rate coefficients

TL;DR

This paper introduces improved collisional ionization equilibrium calculations and a new method for analyzing solar coronal spectra, leading to more accurate estimates of plasma properties and elemental abundances.

Contribution

It presents updated ionization rate coefficients based on state-of-the-art data and a novel approach for determining plasma emission measure and temperature from observations.

Findings

Revised emission measure and electron temperature values differ significantly from previous studies.

Calculated elemental abundance enhancements align with theoretical FIP models.

New ionization data improve the accuracy of coronal plasma diagnostics.

Abstract

We have reanalyzed SUMER observations of a parcel of coronal gas using new collisional ionization equilibrium (CIE) calculations. These improved CIE fractional abundances were calculated using state-of-the-art electron-ion recombination data for K-shell, L-shell, Na-like, and Mg-like ions of all elements from H through Zn and, additionally, Al- through Ar-like ions of Fe. They also incorporate the latest recommended electron impact ionization data for all ions of H through Zn. Improved CIE calculations based on these recombination and ionization data are presented here. We have also developed a new systematic method for determining the average emission measure ($EM$) and electron temperature ($T_e$) of an isothermal plasma. With our new CIE data and our new approach for determining average $EM$ and $T_e$, we have reanalyzed SUMER observations of the solar corona. We have compared our results with those of previous studies and found some significant differences for the derived $EM$ and $T_e$. We have also calculated the enhancement of coronal elemental abundances compared to their photospheric abundances, using the SUMER observations themselves to determine the abundance enhancement factor for each of the emitting elements. Our observationally derived first ionization potential (FIP) factors are in reasonable agreement with the theoretical model of Laming (2008).