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

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 This paper presents unpublished observations made in 2004-2006 of weak polarized lines performed with the Pic du Midi Turret Dome spectropolarimeter, such as atomic lines of Na, Al, H, He,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.