On a limitation of Zeeman polarimetry and imperfect instrumentation in representing solar magnetic fields with weaker polarization signal

TL;DR

This paper discusses the limitations of Zeeman polarimetry and instrumentation in accurately representing weaker solar magnetic fields, highlighting issues with interpreting polarization signals and unresolved structures.

Contribution

It identifies and describes a key limitation in Zeeman polarimetry related to interpreting polarization signals and unresolved magnetic structures in solar observations.

Findings

Zeeman signals differ for line-of-sight and transverse magnetic components.

Unresolved structures and fill fraction affect magnetic field interpretation.

Disambiguation of azimuth introduces additional uncertainties.

Abstract

Full disk vector magnetic fields are used widely for developing better understanding of large-scale structure, morphology, and patterns of the solar magnetic field. The data are also important for modeling various solar phenomena. However, observations of vector magnetic fields have one important limitation that may affect the determination of the true magnetic field orientation. This limitation stems from our ability to interpret the differing character of the Zeeman polarization signals which arise from the photospheric line-of-sight vs. the transverse components of the solar vector magnetic field, and is likely exacerbated by unresolved structure (non-unity fill fraction) as well as the disambiguation of the 180$^\circ$ degeneracy in the transverse-field azimuth. Here we provide a description of this phenomenon, and discuss issues, which require additional investigation.