Atomic physics and modern solar spectro-polarimetry

TL;DR

This paper discusses how atomic transitions can improve solar spectropolarimetry by aiding calibration and diagnostics of magnetic fields, especially with upcoming large telescopes and in the presence of atmospheric distortions.

Contribution

It proposes using specific atomic spectral lines to enable calibration-free magnetic field measurements in solar spectropolarimetry.

Findings

Atomic lines of iron and complex atoms can assist in calibration.

Potential to measure magnetic fields without explicit calibration sequences.

Suggestions for advancing atomic measurements at infrared wavelengths.

Abstract

Observational solar physics is entering a new era with the advent of new 1.5 m class telescopes with adaptive optics, as well as the Daniel K. Inouye 4 m telescope which will become operational in 2019. Major outstanding problems in solar physics all relate to the solar magnetic field. Spectropolarimetry offers the best, and sometimes only, method for accurate measurements of the magnetic field. In this paper we highlight how certain atomic transitions can help us provide both calibration data, as well as diagnostic information on solar magnetic fields, in the presence of residual image distortions through the atmosphere close to, but not at the diffraction limits of large and polarizing telescopes. Particularly useful are spectral lines of neutrals and singly charged ions of iron and other complex atoms. As a proof-of-concept, we explore atomic transitions that might be used to study magnetic fields without the need for an explicit calibration sequence, offering practical solutions to the difficult challenges of calibrating the next generation of solar spectropolarimetric telescopes. Suggestions for additional work on atomic theory and measurements, particularly at infrared wavelengths, are given. There is some promise for continued symbiotic advances between solar physics and atomic physics.