Nonequilibrium Ionization Effects on Synthetic Spectra in the AWSoM Solar Corona

In this work, we combined AWSoM's nonequilibrium ionization (NEI) calculations from Szente et al. with the synthetic spectral computations of SPECTRUM to predict nonequilibrium line intensities across the entire domain of the AWSoM 3D global model. We find that the resulting spectra are strongly affected by nonequilibrium effects in the fast-wind regions and streamer edges and that these effects propagate to narrowband images from SoHO/EIT, SECCHI/EUVI, and SDO/AIA. The dependence shows a different nature for each line observed, resulting in significant changes in line intensity, which need to be accounted for during plasma diagnostics. However, we also find that these effects depend on the local plasma properties, and that no single correction can be developed to account for nonequilibrium effects in observed spectra and images. With a comparison to observational data, we saw that the changes due to NEI, while significant, are not sufficient to account for the differences between Hinode/EIS spectra and AWSoM/SPECTRUM predictions.

Automated summary

In this study, we combined AWSoM's nonequilibrium ionization calculations with synthetic spectral computations to predict nonequilibrium line intensities in the AWSoM 3D global model. The resulting spectra are strongly influenced by nonequilibrium effects in certain regions and propagate to narrowband images from various observation instruments. However, these effects vary depending on the observed line and local plasma properties, making it difficult to develop a single correction for nonequilibrium effects in observed spectra and images. Comparison with observational data showed that the changes due to nonequilibrium ionization are not enough to explain the differences between observed spectra and model predictions.