The polarization of the O VI 1032 A line as a probe for measuring the coronal vector magnetic field via the Hanle effect
Résumé
Recent works have shown the possibility of detecting resonance lines of moderately ionized lithium-like ions (especially O VI 1032 Å) of the chromosphere-corona transition region at high altitudes in the solar corona (up to several solar radii). Since these lines would be partially formed by resonance scattering of the anisotropic underlying transition region radiation field, they are expected to be partially linearly polarized; moreover this polarization should be modified by the local magnetic field (e.g. the Hanle effect). The aim of the present paper is to calculate the expected linear polarization and its modification by the coronal local magnetic field and to provide analytical formulae, in order to investigate the possibility of measuring coronal vector magnetic fields via the interpretation of the Hanle effect.