A Spectroscopic Survey of Infrared 1–4 μm Spectra in Regions of Prominent Solar Coronal Emission Lines of Fe XIII, Si X, and Si IX

Abstract

The infrared solar spectrum contains a wealth of physical data about the Sun and is being explored using modern detectors and technology with new ground-based solar telescopes. One such instrument will be the ground-based Cryogenic Near-IR Spectro-Polarimeter of the Daniel K. Inouye Solar Telescope (DKIST), which will be capable of sensitive imaging of the faint infrared solar coronal spectra with full Stokes I, Q, U, and V polarization states. Highly ionized magnetic dipole emission lines have been observed in galaxies and the solar corona. Quantifying the accuracy of spectral inversion procedures requires a precise spectroscopic calibration of observations. A careful interpretation of the spectra around prominent magnetic dipole lines is essential for deriving physical parameters and particularly for quantifying the off-limb solar coronal observations from DKIST. In this work, we aim to provide an analysis of the spectral regions around the infrared coronal emission lines of Fe xiii 1074.68 nm, Fe xiii 1079.79 nm, Si x 1430.10 nm, and Si ix 3934.34 nm, aligning with the goal of identifying solar photospheric and telluric lines that will help facilitate production of reliable inversions and data products from four sets of solar coronal observations. The outputs can be integrated in processing pipelines to produce level 2 science-ready data.

First Infrared Coronal Spectra from DKIST/Cryo-NIRSP: Comparisons with Global MHD Models

“…Systematic artifacts unique to each bandpass, such as unstable interference fringes or instrument instabilities, can challenge and influence the strategies used to remove the background. Furthermore, each coronal line is partially or significantly blended with photospheric and/or telluric lines, as discussed by Ali et al (2022). Any changes in the scattered spectral profiles between the coronal observations and the calibrations, e.g., line shifts due to changing Doppler velocities or evolution of the telluric absorption, will lead to errors.…”

Thomson Scattering above Solar Active Regions and an Ad Hoc Polarization Correction Method for the Emissive Corona

“…Importantly, we assume that this scattered light can be treated as an unpolarized component of the total signal incident on the optical system and is influenced by the same polarization response matrix. Many important polarized coronal emission lines are located near a photospheric line (Schad & Dima 2020;Ali et al 2022); however, the application of our technique may in some cases be complicated by line blends and/or weak signals. In the event that a suitable photospheric line is unavailable, one may attempt to correct specific components of the crosstalk with other assumptions, at the cost of increased error.…”

Coronagraphic Observations of Si x 1430 nm Acquired by DKIST/Cryo-NIRSP with Methods for Telluric Absorption Correction

“…Dima et al (2019a) and proposed using the Si X line as part of multiline inversions of coronal magnetic fields using full Stokes observations of multiple forbidden lines and/or joint linearly polarized observations of forbidden and permitted lines. Despite these advantages, Si X 1430 nm observations are still sparse, especially outside of solar eclipses, in part due to the challenges introduced by variable atmospheric transmission bands that dominate this spectral window (see Figure 1 and also Ali et al 2022).…”