1201.6312 (Lucia Kleint)
Lucia Kleint
We investigate the decay phase of a C-class flare in full-Stokes imaging
spectropolarimetry with quasi-simultaneous measurements in the photosphere
(6302.5 A line) and in the chromosphere (8542 A line) with the IBIS instrument.
We analyze data from two fields-of-view, each spanning about 40" \times 80" and
targeting the two footpoints of the flare. A region of interest is identified
from V/I images: a patch of opposite polarity in the smaller sunspot's
penumbra. We find unusual flows in this patch at photospheric levels: a Doppler
shift of -4 km/s, but also a possible radial inflow into the sunspot of 4 km/s.
Such patches seem to be common during flares, but only high-resolution
observations allowed us to see the inflow, which may be related to future
flares observed in this region. Chromospheric images show variable overlying
emission and flows and unusual Stokes profiles. We also investigate the
irregular penumbra, whose formation may be blocked by the opposite polarity
patch and flux emergence. The 40 min temporal evolution depicts the larger of
the flare ribbons becoming fainter and changing its shape. Measurable
photospheric magnetic fields remain constant and we do not detect flare energy
transport down from the chromosphere. We find no clear indications of impact
polarization in the 8542 A line. We cannot exclude the possibility of impact
polarization, because weaker signals may be buried in the prominent Zeeman
signatures or it may have been present earlier during the flare.
View original:
http://arxiv.org/abs/1201.6312
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