Abstract
Solar spectro-polarimetry is a powerful tool to investigate the physical processes occurring in the solar atmosphere. The different states of polarization and wavelengths have in fact encoded the information about the thermodynamic state of the solar plasma and the interacting magnetic field. In particular, the radiative transfer theory allows us to invert the spectro-polarimetric data to obtain the physical parameters of the different atmospheric layers and, in particular, of the photosphere. In this work, we present a comparison between two methods used to analyze spectro-polarimetric data: the classical Center of Gravity method in the weak field approximation and an inversion code that solves numerically the radiative transfer equation. The Center of Gravity method returns reliable values for the magnetic field and for the line-of-sight velocity in those regions where the weak field approximation is valid (field strength below 400 G), while the inversion code is able to return the stratification of many physical parameters in the layers where the spectral line used for the inversion is formed.
Highlights
We present a comparison between two methods used to analyze spectro-polarimetric data: the classical Center of Gravity method in the weak field approximation and an inversion code that solves numerically the radiative transfer equation
The Center of Gravity method returns reliable values for the magnetic field and for the line-of-sight velocity in those regions where the weak field approximation is valid, while the inversion code is able to return the stratification of many physical parameters in the layers where the spectral line used for the inversion is formed
The interaction between magnetic fields and convection in the solar photosphere regulates a large variety of physical processes that we can observe from Earth with ground-based solar telescopes
Summary
The interaction between magnetic fields and convection in the solar photosphere regulates a large variety of physical processes that we can observe from Earth with ground-based solar telescopes. There are different methods and approximations to solve it: there are analytical solutions of the RTE based on several assumptions and there are numerical solutions which, using more realistic atmospheric models, return more information about the physical parameters of the atmosphere. We compare the results from the Center of Gravity (CoG) method [2,3,4], based on weak field approximation and an analytical solution of the RTE, and the NICOLE inversion technique [5,6] which solves numerically the RTE.
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