摘要：Context. 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.
Aims. 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.
Methods. 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.
Results. 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.
Conclusions. 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.
