Constraining the magnetic vector in the quiet solar photosphere and the impact of instrumental degradation

Ryan James Campbell, Sergiy Shelyag, Carlos Quintero Noda, Michail Mathioudakis, Peter Keys, Aaron Reid

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Abstract

With the advent of next generation high resolution telescopes, our understanding of how the magnetic field is organized in the internetwork (IN) photosphere is likely to advance.We aim to evaluate the extent to which we can retrieve information about the magnetic vector in the IN photosphere using inversions. We use snapshots produced from high resolution 3D magnetohydrodynamic (MHD) simulations and employ the Stokes Inversions based on Response functions (SIR) code to produce synthetic observables in the near infrared spectral window observed by the GREGOR Infrared Spectrograph (GRIS), which contains the highly magnetically sensitive photospheric Fe I line pair at 15648.52 A and 15652.87 A. We perform nearly 14 million inversions to test how well the true MHD atmospheric parameters can be constrained. Finally, we degrade the synthetic Stokes vectors spectrally and spatially to GREGOR resolutions and examine how this influences observations, considering the impact of stray light, spatial resolution and signal-to-noise (S-to-N). We find the depth-averaged parameters can be recovered by the inversions of the undegraded profiles, and by adding gradients to magnetic field strength, inclination and line of sight velocity we show an improvement in the chi squared value is achieved. We evaluate the extent to which we can constrain these parameters at various optical depths, with the kinematic and thermodynamic parameters sensitive deeper in the atmosphere than the magnetic parameters. We find the S-to-N and spatial resolution play a significant role in determining how the atmosphere appears and the magnetic and kinematic parameters are invariant upon inclusion of unpolarized stray light. We studied a linear polarization feature which resembles those recently observed by GRIS, appearing as loop-like structures with similar magnetic flux density.
Original languageEnglish
JournalAstronomy and Astrophysics
Early online date27 Jul 2021
DOIs
Publication statusEarly online date - 27 Jul 2021

Bibliographical note

Copyright 2021, ESO
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Keywords

  • Solar
  • Infrared
  • Granulation
  • inversions
  • spectropolarimetry
  • magnetic
  • magnetohydrodynamics

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