Internetwork Magnetic Fields Seen in Fe I 1564.8 nm

TL;DR

This study analyzes internetwork magnetic fields in the solar photosphere using full-disk Stokes maps of Fe I 1564.8 nm line from 2010-2019, revealing small-scale, weak, and highly inclined fields with no significant solar cycle variation.

Contribution

It provides a novel analysis of internetwork magnetic fields using moderate-resolution data and a different approach, confirming previous findings with new insights.

Findings

Internetwork fields are small-scale and weak (300-400 G or less).

The fields are highly inclined.

No significant variation over solar cycle 24.

Abstract

We studied the properties of internetwork magnetic fields in the solar photosphere taking advantage of full-disk Stokes $V/I$ maps of the \ion{Fe}{1} 1564.8 nm line, which were obtained during 2010--2019. In contrast to most of the previous studies, we used data with moderate spatial and spectral resolutions. Nonetheless, we were able to distinguish the internetwork field components and the active region / network boundary components using large Zeeman splitting of the \ion{Fe}{1} 1564.8 nm line. Thus, our analysis provides a point of view quite different from that of the previous studies. We analyzed the data statistically without ordinary inversions, yet we successfully derived some properties of internetwork fields; the internetwork is filled with small-scale magnetic fields, their strength is within the weak-field regime of the \ion{Fe}{1} 1564.8 nm line (300--400 G or less), and the internetwork fields are highly inclined. Although the results were obtained from the analysis performed from a different perspective, they are consistent with the majority of the previous findings. In addition, no notable variation in the properties of the internetwork fields was found during the period covering most of solar cycle 24.