Z. Xu, A. Lagg, S. Solanki, Y. Liu
Vector magnetic fields of an active region filament in the photosphere and
upper chromosphere are obtained from spectro-polarimetric observations recorded
with the Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower
Telescope (VTT). We apply Milne-Eddington inversions on full Stokes vectors of
the photospheric Si I 1082.7 nm and the upper chromospheric He I triplet at
1083.0 nm to obtain magnetic field vector and velocity maps in two atmosphere
layers. We find that: (1)A complete filament was already present in H$\alpha$
at the beginning of the TIP II data acquisition. Only a partially formed one,
composed of multiple small threads, was present in He I. (2) The AR filament
comprises two sections. One shows strong magnetic field intensities, about 600
- 800 G in the upper chromosphere and 800 - 1000 G in the photosphere. The
other exhibits only comparatively weak magnetic field strengths in both layers.
(3) The Stokes V signal is indicative of a dip in the magnetic field strength
close to the chromospheric PIL. (3) In the chromosphere consistent upflows are
found along the PIL flanked by downflows. (4) The transversal magnetic field is
nearly parallel to the PIL in the photosphere and inclined by 20 - 30 degree in
the chromosphere. (5) The chromospheric magnetic field around the filament is
found to be in normal configuration, while the photospheric field presents a
concave magnetic topology. The observations are consistent with the emergence
of a flux rope with a subsequent formation of a filament.
View original:
http://arxiv.org/abs/1202.4562
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