The influence of photo-induced processes and charge transfer on carbon and oxygen in the lower solar atmosphere

TL;DR

This study investigates how photo-induced processes and charge transfer affect atomic ionization and emission lines of carbon and oxygen in the lower solar atmosphere, aiming to improve the accuracy of solar atmospheric models.

Contribution

It introduces additional atomic processes such as radiation-induced excitation, ionization, and charge transfer into solar atmospheric models, addressing existing discrepancies in emission predictions.

Findings

Enhanced modeling of ion charge states and level populations.

Altered line emission predictions for low charge states.

Insights into atomic processes affecting solar atmosphere emission.

Abstract

To predict line emission in the solar atmosphere requires models which are fundamentally different depending on whether the emission is from the chromosphere or the corona. At some point between the two regions, there must be a change between the two modelling regimes. Recent extensions to the coronal modelling for carbon and oxygen lines in the solar transition region have shown improvements in the emission of singly- and doubly-charged ions, along with Li-like ions. However, discrepancies still remain, particularly for singly-charged ions and intercombination lines. The aim of this work is to explore additional atomic processes that could further alter the charge state distribution and the level populations within ions, in order to resolve some of the discrepancies. To this end, excitation and ionisation caused by both the radiation field and by atom-ion collisions have been included, along with recombination through charge transfer. The modelling is carried out using conditions which would be present in the quiet Sun, which allows an assessment of the part atomic processes play in changing coronal modelling, separately from dynamic and transient events taking place in the plasma. The effect the processes have on the fractional ion populations are presented, as well as the change in level populations brought about by the new excitation mechanisms. Contribution functions of selected lines from low charge states are also shown, to demonstrate the extent to which line emission in the lower atmosphere could be affected by the new modelling.