Observations of the forward scattering Hanle effect in the Ca I 4227 Å line
Abstract
Chromospheric magnetic fields are notoriously difficult 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 10 830 Å and the Ca i 4227 Å 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 Å 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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2011
- DOI:
- 10.1051/0004-6361/201117047
- arXiv:
- arXiv:1105.2157
- Bibcode:
- 2011A&A...530L..13B
- Keywords:
-
- magnetic fields;
- polarization;
- scattering;
- Sun: chromosphere;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 4 pages, 5 figures, to be published as a Letter in Astronomy &