Inference of magnetic fields in inhomogeneous prominences

Abstract

Most of the quantitative information about the magnetic field vector in solar prominences comes from the analysis of the Hanle effect acting on lines formed by scattering. As these lines can be of non-negligible optical thickness, it is of interest to study the line formation process further. We investigate the multidimensional effects on the interpretation of spectropolarimetric observations, particularly on the inference of the magnetic field vector. We do this by analyzing the differences between multidimensional models, which involve fully self-consistent radiative transfer computations in the presence of spatial inhomogeneities and velocity fields, and those which rely on simple one-dimensional geometry. We study the formation of a prototype line in ad hoc inhomogeneous, isothermal 2D prominence models. We solve the NLTE polarized line formation problem in the presence of a large-scale oriented magnetic field. The resulting polarized line profiles are then interpreted (i.e. inverted) assuming a simple 1D slab model. We find that differences between input and the inferred magnetic field vector are non-negligible. Namely, we almost universally find that the inferred field is weaker and more horizontal than the input field. Spatial inhomogeneities and radiative transfer have a strong effect on scattering line polarization in the optically thick lines. In real-life situations, ignoring these effects could lead to a serious misinterpretation of spectropolarimetric observations of chromospheric objects such as prominences.

11 pages, 9 figures

References in corpus (6)

• Advanced Forward Modeling and Inversion of Stokes Profiles Resulting from the Joint Action of the Hanle and Zeeman Effects
• The magnetic field configuration of a solar prominence inferred from spectropolarimetric observations in the He I 10830 A triplet
• Three-dimensional radiative transfer simulations of the scattering polarization of the hydrogen Ly$\alpha$ line in a MHD model of the chromosphere-corona transition region
• The Scattering Polarization of the Sr I 4607 ÅLine at the Diffraction Limit Resolution of a 1-m Telescope
• Chromospheric diagnosis with Ca II lines: forward modeling in forward scattering (I)
• Effect of motions in prominences on the helium resonance lines in the extreme ultraviolet

Cited by in corpus (2)

• Spectropolarimetric analysis of an active region filament. I. Magnetic and dynamical properties from single component inversions
• Spectropolarimetric analysis of an active region filament. II. Evidence of the limitations of a single component model