Using the Stokes V widths of Fe I lines for diagnostics of the intrinsic solar photospheric magnetic field

TL;DR

This study introduces a new method using Stokes V widths of Fe I spectral lines to diagnose the solar photospheric magnetic field, demonstrating its effectiveness across various lines and field strengths.

Contribution

The paper develops and tests a novel Stokes V widths method for magnetic field diagnostics, offering an alternative to traditional line ratio techniques.

Findings

Fe I 6301 line is most effective, sensitive over ~200G to 2kG.

Method works with various optical and near-infrared lines.

Effective in narrower field ranges for other lines.

Abstract

The goal of this study is to explore a novel method for the solar photospheric magnetic field diagnostics using Stokes V widths of different magnetosensitive Fe~I spectral lines. We calculate Stokes I and V profiles of several Fe I lines based on a one-dimensional photospheric model VAL C using the NICOLE radiative transfer code. These profiles are used to produce calibration curves linking the intrinsic magnetic field values with the widths of blue peaks of Stokes V profiles. The obtained calibration curves are then tested using the Stokes profiles calculated for more realistic photospheric models based on MHD models of magneto-convection. It is shown that the developed Stokes V widths (SVW) method can be used with various optical and near-infrared lines. Out of six lines considered in this study, FeI 6301 line appears to be the most effective: it is sensitive to fields over ~200G and does not show any saturation up to ~2kG. Other lines considered can also be used for the photospheric field diagnostics with this method, however, only in narrower field value ranges, typically from about 100G to 700-1000G. The developed method can be a useful alternative to the classical magnetic line ratio method, particularly when the choice of lines is limited.