Spectroscopic Observations of the Solar Corona in the Visible and Extreme Ultraviolet during the 2017 Total Solar Eclipse

Total solar eclipses (TSEs) are one of the best opportunities to study the elemental composition and plasma properties of the solar corona within 2-3 Rs above the solar surface. In this study, we present spectroscopic observations of the solar corona acquired during the 2017 August 21 TSE with a three-channel partially multiplexed imaging spectrometer operating at extremely high orders (> 50). The field of view covered a 4 Rs North-South slit span, originating close to the central meridian, which scanned a heliocentric distance of ~1.5 Rs off the west limb throughout totality. The line widths and Doppler shifts of the Fe X (637.4 nm) and Fe XIV (530.3 nm) emission, when present, yielded effective ion temperatures (Teff) and speeds along the line of sight in different coronal structures such as active regions, streamers, and coronal holes. We found the Teff of Fe XIV in the streamer ranges from 4 to 5 MK, which is higher than the Teff in the active region (2.5-3 MK). We also confirmed an increase in the Fe X line width between 1.0 to 1.3 Rs in the polar coronal hole. The plasma diagnostics inferred from the eclipse emission line profiles are consistent with emission line profiles of the extreme ultraviolet (EUV) lines (e.g., Fe X 18.45 nm and Fe XIV 264.8 nm) in a small quiet Sun (QS) region close to the east limb and in the north pole coronal hole. Moreover, we successfully reproduced the observed Fe XIV Doppler shifts and line widths with the Alfvén Wave Solar Model (AWSoM). This study underscores the importance and feasibility of spectroscopic observations during the TSE and encourages similar observations during the 2024 Great American Eclipse.