A new MHD-assisted Stokes inversion technique

TL;DR

This paper introduces a novel MHD-assisted Stokes inversion method that leverages synthetic MHD profiles to derive physically consistent atmospheric parameters from spectropolarimetric data, improving accuracy over traditional techniques.

Contribution

The new technique combines MHD simulations with spectral synthesis to perform Stokes inversions, enabling physically consistent atmospheric parameters and iterative refinement.

Findings

Achieved a 2.2-fold reduction in mean chi-squared value after iterative refinement.

Provided atmospheric parameters on a geometrical height scale.

Produced physically consistent MHD data sets matching observations.

Abstract

We present a new method of Stokes inversion of spectropolarimetric data and evaluate it by taking the example of a SUNRISE/IMaX observation. An archive of synthetic Stokes profiles is obtained by the spectral synthesis of state-of-the-art magnetohydrodynamics (MHD) simulations and a realistic degradation to the level of the observed data. The definition of a merit function allows the archive to be searched for the synthetic Stokes profiles that match the observed profiles best. In contrast to traditional Stokes inversion codes, which solve the Unno-Rachkovsky equations for the polarized radiative transfer numerically and fit the Stokes profiles iteratively, the new technique provides the full set of atmospheric parameters. This gives us the ability to start an MHD simulation that takes the inversion result as initial condition. After a relaxation process of half an hour solar time we obtain physically consistent MHD data sets with a target similar to the observation. The new MHD simulation is used to repeat the method in a second iteration, which further improves the match between observation and simulation, resulting in a factor of 2.2 lower mean $\chi^2$ value. One advantage of the new technique is that it provides the physical parameters on a geometrical height scale. It constitutes a first step towards inversions giving results consistent with the MHD equations.