Chromospheric Polarization in the Photospheric Solar Oxygen Infrared Triplet

TL;DR

This study models the scattering polarization in the solar oxygen infrared triplet, revealing its formation in the chromosphere and its sensitivity to magnetic fields, thus providing insights into solar chromospheric magnetism.

Contribution

It demonstrates that the polarization signals in the oxygen triplet originate in the chromosphere and are sensitive to weak magnetic fields, offering a new diagnostic tool.

Findings

Polarization forms in the chromosphere, above the photosphere.

Signals encode information about weak magnetic fields via the Hanle effect.

Modeling matches observed polarization patterns.

Abstract

We present multilevel radiative transfer modeling of the scattering polarization observed in the solar O I infrared triplet around 777 nm. We demonstrate that the scattering polarization pattern observed on the solar disk forms in the chromosphere, far above the photospheric region where the bulk of the emergent intensity profiles originates. We study the sensitivity of the polarization pattern to the thermal structure of the solar atmosphere and to the presence of weak magnetic fields (0.01 - 100 G) through the Hanle effect, showing that the scattering polarization signals of the oxygen infrared triplet encode information on the magnetism of the solar chromosphere.