Vector Magnetic Field in Prominences: Observations and Analysis

Abstract

Measurements of the polarization of the He I D3 multiplet in a prominence allow the magnetic fields associated with the prominence to be deduced. The amount and angle of the linear polarization are governed by the Hanle effect, the detailed theory of which is applied to the Stokes components of the He I D3 emission to derive the associated vector magnetic fields. The dependence of the observed polarizaion on the magnetic field is predicted from solutions of the statistical equilibrium equations for the He I D3 multiplet. Magnetic field vector solutions for each pair of linear polarization Stokes profiles corresponding to an observational point in a prominence are not uniquely determined. Nevertheless, physically correct solutions can usually be identified with a high confidence level. Field vectors are mostly close to horizontal and normal to the prominence surface, magnitudes ranging from 6 G to 60 G, with a mean of 24 G.