Volume 530, June 2011
|Number of page(s)||4|
|Published online||24 May 2011|
Letter to the Editor
Observations of the forward scattering Hanle effect in the Ca I 4227 Å line
Istituto Ricerche Solari Locarno, via Patocchi,
2 Institute of Astronomy, ETH Zürich, 8093 Zürich, Switzerland
3 Indian Institute of Astrophysics, Koramangala, Bangalore 560 034, India
4 MPI für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany
5 UNS, CNRS, OCA, Laboratoire Cassiopée, 06304 Nice Cedex, France
Received: 7 April 2011
Accepted: 5 May 2011
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.
Key words: magnetic fields / polarization / scattering / Sun: chromosphere
© ESO, 2011
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