Effect of the anomalous dispersion in the solar atmosphere on results of magnetic field measurements by the line-ratio method

TL;DR

This paper analyzes how anomalous dispersion affects solar magnetic field measurements using the line-ratio method, highlighting conditions under which it must be considered for accurate results.

Contribution

It provides a detailed analysis of the impact of anomalous dispersion on the line-ratio method in solar magnetic field measurements, specifying when corrections are necessary.

Findings

Anomalous dispersion affects measurements when magnetic inclination is within 20 degrees.

The effect is significant for magnetic fields stronger than 100 mT.

Consideration of anomalous dispersion is necessary near line centers (<4 pm).

Abstract

On the basis of Stokes parameter calculations for the Fe I 524.7 and 525.0 nm lines and the Holweger-Muller model atmosphere, the effect of the anomalous dispersion on solar magnetic field measurements by the line-ratio method is analyzed. It is shown that with the present-day observational accuracy the anomalous dispersion should be taken into consideration in the line-ratio method only when the following four conditions are fulfilled simultaneously: a) the inclination of the magnetic lines to the line of sight does not exceed 20 degrees; b) the magnetic field strength is larger than 100 mT; c) the cross profile of the magnetic field in subtelescopic flux tubes is rectangular; and d) the parts of the magnetically sensitive line profiles close to the line center (<4 pm) are used.