Diagnostic capabilities of spectropolarimetric observations for understanding solar phenomena I. Zeeman-sensitive photospheric lines
arXiv:2106.05084 · doi:10.1051/0004-6361/202037735
Abstract
Future ground-based telescopes will expand our capabilities for simultaneous multi-line polarimetric observations in a wide range of wavelengths, from the near-ultraviolet to the near-infrared. This creates a strong demand to compare candidate spectral lines to establish a guideline of the lines that are most appropriate for each observation target. We focused in this first work on Zeeman-sensitive photospheric lines in the visible and infrared. We first examined their polarisation signals and response functions using a 1D semi-empirical atmosphere. Then we studied the spatial distribution of the line core intensity and linear and circular polarisation signals using a realistic 3D numerical simulation. We ran inversions of synthetic profiles, and we compared the heights at which we obtain a high correlation between the input and the inferred atmosphere. We also used this opportunity to revisit the atomic information we have on these lines and computed the broadening cross-sections due to collisions with neutral hydrogen atoms for all the studied spectral lines. The results reveal that four spectral lines stand out from the rest for quiet-Sun and network conditions: Fe I 5250.2, 6302, 8468, and 15648 A. The first three form higher in the atmosphere, and the last line is mainly sensitive to the atmospheric parameters at the bottom of the photosphere. However, as they reach different heights, we strongly recommend using at least one of the first three candidates together with the Fe I 15648 A line to optimise our capabilities for inferring the thermal and magnetic properties of the lower atmosphere.
15 pages, 12 figures, regular publication
References in corpus (13)
- The Solar Optical Telescope for the Hinode Mission: An Overview
- Astrophysics Source Code Library
- Spectral Line Selection for HMI: A Comparison of Fe I 6173 and Ni I 6768
- Non-LTE inversions of the Mg II h&k and UV triplet lines
- Ellerman bombs and UV bursts: transient events in chromospheric current sheets
- Internetwork magnetic field distribution from simultaneous 1.56 micron and 630 nm observations
- The Hanle and Zeeman polarization signals of the solar Ca II 8542 Å line
- The influence of NLTE effects in Fe I lines on an inverted atmosphere I. 6301 A and 6302 A lines formed in 1D NLTE
- Chromospheric polarimetry through multi-line observations of the 850 nm spectral region
- Solar polarimetry through the K I lines at 770 nm
- Probing photospheric magnetic fields with new spectral line pairs
- Spatio-temporal evolution of Hanle and Zeeman synthetic polarization in a chromospheric spectral line
- The polarization signature of photospheric magnetic fields in 3D MHD simulations and observations at disk center