A spectroscopic survey of infrared 1-4μm 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 that 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 will be integrated in the processing pipeline to produce Level-2 science-ready data that will be made available to DKIST observers.

Thomson scattering above solar active regions and an ad-hoc polarization correction method for the emissive corona

“…Importantly, we assume this scattered light can be treated as an unpolarized component of the total signal incident on the optical system and 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 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.…”