Linear polarization of hydrogen Balmer lines in optically thick prominences: theoretical investigation.
Résumé
The expected linear polarization in Hα for a filament observed at different positions over the solar disk is investigated from a theoretical point of view. The filament is schematized as an infinite cylinder with an elliptical cross-section standing horizontally on the solar surface. The emerging linear polarization is calculated according to a perturbative scheme introduced in a preceding paper (Landi Degl'Innocenti et al., 1987). The role of depolarizing collisions and the influence of local magnetic fields (Hanle effect) is fully accounted for. Typical results are presented for the expected Hα polarization across filaments observed at various positions and skew angles over the solar disk.