Observations of the Joint Action of the Hanle and Zeeman Effects in the D2 Line of BaII

TL;DR

This paper presents high-sensitivity spectropolarimetric observations of the Ba II D2 line near the solar limb, demonstrating the combined effects of Hanle and Zeeman phenomena for diagnosing magnetic fields in the solar chromosphere.

Contribution

It provides detailed observational evidence of the joint Hanle and Zeeman effects in the Ba II D2 line, validating theoretical models and highlighting its diagnostic potential.

Findings

Clear signatures of Hanle and Zeeman effects observed

Effective for magnetic field diagnostics from 1 G to kG

Qualitative agreement with theoretical expectations

Abstract

We show a selection of high-sensitivity spectropolarimetric observations obtained over the last few years in the Ba II D2-line with the Zurich Imaging Polarimeter (ZIMPOL) attached to the Gregory Coude Telescope of IRSOL. The measurements were collected close to the solar limb, in several regions with varying degree of magnetic activity. The Stokes profiles we have observed show clear signatures of the joint action of the Hanle and Zeeman effects, in very good qualitative agreement with the theoretical expectations. Polarimetric measurements of this line show to be very well suited for magnetic field diagnostics of the lower solar chromosphere, from regions with field intensities as low as 1 gauss to strongly magnetized ones having kG field strengths.