A new MHD-assisted Stokes inversion technique

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.

Accepted for publication in the Astrophysical Journal on Nov. 15 2016 (part of the Sunrise2 special issue)

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• Stokes Inversion based on Convolutional Neural Networks
• Slender Ca II H Fibrils Mapping Magnetic Fields in the Low Solar Chromosphere
• FIRTEZ-dz: A Forward and Inverse solver of the polarized Radiative Transfer Equation under Zeeman regime in geometrical scale
• Magneto-static modelling from SUNRISE/IMaX: Application to an active region observed with SUNRISE II
• Mimicking spectropolarimetric inversions using convolutional neural networks
• The potential of many-line inversions of photospheric spectropolarimetric data in the visible and near UV
• Morphological properties of slender Ca II H fibrils observed by SUNRISE II
• Combining magneto-hydrostatic constraints with Stokes profile inversions. II. Application to Hinode/SP observations
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• Intensity contrast of solar plage as a function of magnetic flux at high spatial resolution
• Inference of electric currents in the solar photosphere
• Power spectrum of turbulent convection in the solar photosphere
• The polarization signature of photospheric magnetic fields in 3D MHD simulations and observations at disk center
• Magnetic Imaging of the Outer Solar Atmosphere (MImOSA): Unlocking the driver of the dynamics in the upper solar atmosphere