Weak polarized lines of the second solar spectrum (Na, Al, H, He, Ti, Li, Sc, C2 and MgH) observed at the Pic du Midi turret dome

TL;DR

This paper reports observations of weak polarized lines in the second solar spectrum, focusing on lines of various elements and molecules near the solar limb, using data from the Pic du Midi spectropolarimeter.

Contribution

It presents new observational data of faint polarized lines in the second solar spectrum, expanding the understanding of solar polarization features.

Findings

Detected weak polarization signals (<0.3%) in multiple atomic and molecular lines.

Provided new measurements of polarized lines of Na, Al, H, He, Ti, Li, Sc, C2, and MgH.

Enhanced the spectral database of the second solar spectrum with unpublished observations.

Abstract

The second solar spectrum is the solar spectrum of Stokes parameter Q observed in linear polarization close to the solar limb. It differs significantly of the usual intensity spectrum (Stokes parameter I). The second solar spectrum contains in the visible range a few polarized lines with Q/I > 1% (such as CaI, SrI, SrII, BaII), but most lines exhibit weak or very faint polarization rates (Q/I < 0.3%). This paper presents unpublished observations made in 2004-2006 of weak polarized lines performed with the Pic du Midi Turret Dome spectropolarimeter, such as atomic lines of Na, Al, H, He, Ti, Li, Sc as well as C2 and MgH molecules.