Multi-dimensional radiative transfer to analyze Hanle effect in Ca {\sc ii} K line at 3933 \AA\,

TL;DR

This study applies multi-dimensional polarized radiative transfer modeling, including Hanle effect and partial frequency redistribution, to analyze the Ca II K line in the solar chromosphere, revealing the impact of atmospheric inhomogeneities on polarization.

Contribution

First application of multi-D polarized radiative transfer with Hanle effect and PRD to chromospheric lines using MHD simulations.

Findings

Horizontal inhomogeneities cause strong polarization variations in line wings.

Homogeneous models produce uniform polarization in line core.

Multi-D effects are crucial for accurate polarization modeling.

Abstract

Radiative transfer (RT) studies of the linearly polarized spectrum of the Sun (the second solar spectrum) have generally focused on the line formation, with an aim to understand the vertical structure of the solar atmosphere using one-dimensional (1D) model atmospheres. Modeling spatial structuring in the observations of the linearly polarized line profiles requires the solution of multi-dimensional (multi-D) polarized RT equation and a model solar atmosphere obtained by magneto-hydrodynamical (MHD) simulations of the solar atmosphere. Our aim in this paper is to analyze the chromospheric resonance line Ca {\sc ii} K at 3933 \AA\ using multi-D polarized RT with Hanle effect and partial frequency redistribution in line scattering. We use an atmosphere which is constructed by a two-dimensional snapshot of the three-dimensional MHD simulations of the solar photosphere, combined with columns of an 1D atmosphere in the chromosphere. This paper represents the first application of polarized multi-D RT to explore the chromospheric lines using multi-D MHD atmospheres, with PRD as the line scattering mechanism. We find that the horizontal inhomogeneities caused by MHD in the lower layers of the atmosphere are responsible for strong spatial inhomogeneities in the wings of the linear polarization profiles, while the use of horizontally homogeneous chromosphere (FALC) produces spatially homogeneous linear polarization in the line core.