Diagnostic capabilities of spectropolarimetric observations for understanding solar phenomena I. Zeeman-sensitive photospheric lines. (arXiv:2106.05084v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Noda_C/0/1/0/all/0/1">C. Quintero Noda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barklem_P/0/1/0/all/0/1">P. S. Barklem</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gafeira_R/0/1/0/all/0/1">R. Gafeira</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cobo_B/0/1/0/all/0/1">B. Ruiz Cobo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Collados_M/0/1/0/all/0/1">M. Collados</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carlsson_M/0/1/0/all/0/1">M. Carlsson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pillet_V/0/1/0/all/0/1">V. Martínez Pillet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Suarez_D/0/1/0/all/0/1">D. Orozco Suárez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Uitenbroek_H/0/1/0/all/0/1">H. Uitenbroek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Katsukawa_Y/0/1/0/all/0/1">Y. Katsukawa</a>
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.
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.
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