Identification of spectral lines to study CMEs with ground- and space-based observatories

Many studies of coronal mass ejections (CMEs) suggest that the plasma experiences rapid and significant heating as it travels away from the Sun. However, the dynamic and multi-thermal nature of the eruption makes it difficult to study the plasma's temporal evolution with a single EUV channel or spectral line. Therefore, in this work, we identify useful spectral lines for CME diagnostics. We include lines spanning the extreme ultraviolet to near-Infrared, 100-14400 Å, that range between log T_e (K) = 4 - 6.7 in equilibrium formation temperature to study the eruption. Many lines tested in our analysis will be observed by future ground based solar telescopes; DKIST, and UCoMP, and space-based EUV spectrometer SPICE on Solar Orbiter.

The synthetic intensities for each line were computed between 1.05-2R_sun from a CME comprised of a prominence, prominence-coronal transition region (PCTR), and coronal plasma: an empirical model of their thermodynamic properties was developed in a previous study. We find many of the lines from the prominence material maintain strong signal and remain in ionization equilibrium throughout the field of view considered. The intensities formed within the strongly heated, tenuous PCTR plasma peak and subsequently dim following the rapid ionization of the corresponding emitting ion while evolving far from ionization equilibrium. Furthermore, we find each component can be observed by multiple instruments providing the opportunity to make coordinated plasma measurements. We include a summary of spectral lines that are predicted to be visible from each CME component and discuss their diagnostic potential