Molecular Line Polarization in the Solar Atmosphere: MGH Lines

Abstract

The polarimetric observations of the quiet Sun show linear polarization in molecular lines of C_2, MgH, etc. The molecular lines are very faint in the intensity spectrum. We propose that the polarization is caused by coherent scattering processes in the solar atmosphere as in the case of atomic lines. The intensity and polarization profiles of MgH lines are calculated using the quiet-Sun model by Vernazza, Avrett, & Loeser. This procedure allows us to estimate the oscillator strengths (f), the inelastic collisional rates (Γ_I), and the depolarizing elastic collision rates (D^(2)) for the molecular line transitions in the solar atmosphere. It is found that for the line λ5165.933, f=0.04, Γ_I=1.85x10^7 s^-1, and D^(2)=9.52x10^6 s^-1. The line λ5168.147 fits the observations for f=0.05, Γ_I=2.91x10^7 s^-1, and D^(2)=3.69x10^7 s^-1.