Chromospheric magnetic fields are notoriously diffcult to measure. The chromospheric lines are broad, while the fields are producing a minuscule Zeeman-effect polarization. A promising diagnostic alternative is provided by the forward-scattering Hanle effect, which can be recorded in chromospheric lines such as the He i 10830 {\AA} and the Ca i 4227 {\AA} lines. We present a set of spectropolarimetric observations of the full Stokes vector obtained near the center of the solar disk in the Ca i 4227 {\AA} line with the ZIMPOL polarimeter at the IRSOL observatory.We detect a number of interesting forward-scattering Hanle effect signatures, which we model successfully using polarized radiative transfer. Here we focus on the observational aspects, while a separate companion paper deals with the theoretical modeling.
@article{arxiv.1105.2157,
title = {Observations of the forward scattering Hanle effect in the Ca i 4227 {\AA} line},
author = {M. Bianda and R. Ramelli and L. S. Anusha and J. O. Stenflo and K. N. Nagendra and R. Holzreuter and M. Sampoorna and H. Frisch and H. N. Smitha},
journal= {arXiv preprint arXiv:1105.2157},
year = {2015}
}
Comments
4 pages, 5 figures, to be published as a Letter in Astronomy & Astrophysics