Spectropolarimetric analysis of an active region filament. I. Magnetic and dynamical properties from single component inversions

TL;DR

This study investigates the magnetic and dynamic properties of an active region filament using spectropolarimetric data and single component inversions, revealing limitations of simple models and suggesting the need for more complex analysis.

Contribution

It provides a detailed spectropolarimetric analysis of an active region filament and highlights the limitations of single component inversions in accurately determining magnetic fields.

Findings

Stokes V map does not clearly show filament signatures.

Azimuth map patterns suggest influence from underlying active region fields.

Indications that more complex inversion models are necessary.

Abstract

The determination of the magnetic filed vector in solar filaments is possible by interpreting the Hanle and Zeeman effects in suitable chromospheric spectral lines like those of the He I multiplet at 10830 A. We study the vector magnetic field of an active region filament (NOAA 12087). Spectropolarimetric data of this active region was acquired with the GRIS instrument at the GREGOR telescope and studied simultaneously in the chromosphere with the He I 10830 A multiplet and in the photosphere with the Si I 10827 A line. As it is usual from previous studies, only a single component model is used to infer the magnetic properties of the filament. The results are put into a solar context with the help of the Solar Dynamic Observatory images. Some results clearly point out that a more complex inversion had to be done. Firstly, the Stokes $V$ map of He I does not show any clear signature of the presence of the filament. Secondly, the local azimuth map follows the same pattern than Stokes $V$ as if the polarity of Stokes $V$ were conditioning the inference to very different magnetic field even with similar linear polarization signals. This indication suggests that the Stokes $V$ could be dominated by the below magnetic field coming from the active region, and not, from the filament itself. Those and more evidences will be analyzed in depth and a more complex inversion will be attempted in the second part of this series.