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A&A 481, L13-L16 (2008)
DOI: 10.1051/0004-6361:20079002
Letter
Evidence of magnetic field wrapping around penumbral filaments
J. M. Borrero1, B. W. Lites1, and S. K. Solanki21 High Altitude Observatory, National Center for Atmospheric Research ( The National Center for Atmospheric Research in sponsored by the National Science Foundation.) , Center Green Dr. CG-1, Boulder CO, 80301, USA
e-mail: [borrero;lites]@ucar.edu
2 Max Planck Institut für Sonnensystemforshung, Max Planck Strasse 2, 37191 Katlenburg-Lindau, Germany
e-mail: solanki@mps.mpg.de
(Received 6 November 2007 / Accepted 15 December 2007)
Abstract
We employ high-spatial resolution spectropolarimetric observations from
the Solar Optical Telescope on-board the Hinode spacecraft to investigate the fine
structure of the penumbral magnetic fields. The Stokes vector of two neutral iron lines
at 630 nm is inverted at every spatial pixel to retrieve the depth-dependence of
the magnetic field vector, line-of-sight velocity and thermodynamic parameters.
We show that the azimuthal angle of the magnetic field vector has opposite sign
on both sides above the penumbral filaments. This is consistent with the wrapping
of an inclined field around the horizontal filaments. The wrapping effect is
stronger for filaments with larger horizontal extensions. In addition, we find that
the external magnetic field can penetrate into the intraspines, leading to
non-radial magnetic fields inside them. These findings shed
some light on the controversial small-scale structure of the sunspot penumbra.
Key words: sunspots -- Sun: magnetic fields -- Sun: photosphere
© ESO 2008