Quiet-Sun and Coronal Hole in \ion{Mg}{2}~k line as observed by IRIS

Abstract

Coronal holes (CHs) regions are dark in comparison to the quiet-Sun (QS) at the coronal temperatures. However, at chromospheric and transition region (TR) temperatures, QS and CHs are hardly distinguishable. In this study we have used the \ion{Mg}{2}~2796.35~Å spectral line recorded by the Interface Region Imaging Spectrometer (IRIS) to understand the similarities and differences in the QS and CH at chromospheric levels. Our analysis reveals that the emission from \ion{Mg}{2}~k3 \& k2v that originates in the chromosphere is significantly lower in CH than in QS for the regions with similar magnetic field strength. The wing emissions of \ion{Mg}{2}~k that originates from the photospheric layer, however, do not show any difference between QS and CH. The difference in \ion{Mg}{2}~k3 intensities between QS and CH increases with increasing magnetic field strength. We further studied the effects of spectral resolution on these differences and found that the difference in the intensities decreases with decreasing spectral resolution. For a resolution of 11~Å, the difference completely disappears. These findings are not only important for mass and energy supply from the chromosphere to the corona but also provides essential ingredients for the modelling of the solar spectral irradiance for the understanding of the Sun-climate relationships.

14 figures, Accepted for publication in the Astrophysical Journal

References in corpus (5)

• Similarities and Differences between Coronal Holes and the Quiet Sun: Are Loop Statistics the Key?
• The influence of coronal EUV irradiance on the emission in the He I 10830 A and D3 multiplets
• Observed Variability of the Solar Mg II h Spectral Line
• The cause of spatial structure in solar He I 1083 nm multiplet images
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• Impact of thermal misbalance on acoustic-gravity waves in the solar atmosphere
• Asymmetry of the spectral lines of the coronal hole and quiet Sun in the transition region
• Ca ii 854.2 nm in an enhanced network region simulated with MURaM-ChE
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)