Bibcode
Felipe, T.; Collados, M.; Khomenko, E.; Kuckein, C.; Asensio Ramos, A.; Balthasar, H.; Berkefeld, T.; Denker, C.; Feller, A.; Franz, M.; Hofmann, A.; Joshi, J.; Kiess, C.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pastor Yabar, A.; Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T.
Bibliographical reference
Astronomy and Astrophysics, Volume 596, id.A59, 13 pp.
Advertised on:
11
2016
Journal
Citations
46
Refereed citations
45
Description
Context. Active regions are the most prominent manifestations of solar
magnetic fields; their generation and dissipation are fundamental
problems in solar physics. Light bridges are commonly present during
sunspot decay, but a comprehensive picture of their role in the removal
of the photospheric magnetic field is still lacking. Aims: We
study the three-dimensional configuration of a sunspot, and in
particular, its light bridge, during one of the last stages of its
decay. Methods: We present the magnetic and thermodynamical
stratification inferred from full Stokes inversions of the photospheric
Si i 10 827 Å and Ca i 10 839 Å lines obtained with the
GREGOR Infrared Spectrograph of the GREGOR telescope at the Observatorio
del Teide, Tenerife, Spain. The analysis is complemented by a study of
continuum images covering the disk passage of the active region, which
are provided by the Helioseismic and Magnetic Imager on board the Solar
Dynamics Observatory. Results: The sunspot shows a light bridge
with penumbral continuum intensity that separates the central umbra from
a smaller umbra. We find that in this region the magnetic field lines
form a canopy with lower magnetic field strength in the inner part. The
photospheric light bridge is dominated by gas pressure (high-β), as
opposed to the surrounding umbra, where the magnetic pressure is higher.
A convective flow is observed in the light bridge. This flow is able to
bend the magnetic field lines and to produce field reversals. The field
lines merge above the light bridge and become as vertical and strong as
in the surrounding umbra. We conclude that this occurs because two
highly magnetized regions approach each other during the sunspot
evolution.
Movies associated to Figs. 2 and 13 are available at http://www.aanda.org