Nonthermal Velocities in a Quiescent Active Region and Quiet Sun Area Observed by EUNIS: Implications for Coronal Heating

The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument observed spectral line emission in a short wavelength (SW) channel at 92-115 A in 3rd order and 277-345 A in 1st order, and in a long wavelength (LW) channel at 525-639 A in 1st order. These wavebands include hundreds of lines formed at temperatures that range from several tens of thousands of degrees to 10 MK, and include lines from Fe XVIII at 93.932 and 103.948 A, and from Fe XIX at 108.355 and 592.236 A. Here we focus on measurements of nonthermal Doppler velocities in quiescent AR 12824 and quiet area observed during the flight of 2021 May 18. We find that nonthermal velocities are independent of line formation temperature in both the active region and the quiet area, and lie within the range 45 ± 6 km/s. Comparisons are made with coordinated observations from EIS, as well as with predictions from models of a nanoflare-heated corona. EUNIS was supported by NASA Heliophysics Low Cost Access to Space award 13-HTIDS13_2-0074.