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Three-dimensional structure of a sunspot light bridge
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Number of Authors: 30
2016 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 596, A59Article in journal (Refereed) Published
Abstract [en]

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 angstrom and Ca I 10 839 angstrom 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-beta), 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.

Place, publisher, year, edition, pages
2016. Vol. 596, A59
Keyword [en]
Sun: photosphere, Sun: magnetic fields, sunspots, methods: data analysis, methods: observational, Sun: activity
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-139438DOI: 10.1051/0004-6361/201629586ISI: 000390797900111OAI: oai:DiVA.org:su-139438DiVA: diva2:1077257
Available from: 2017-02-27 Created: 2017-02-27 Last updated: 2017-02-27Bibliographically approved

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Joshi, Jayant
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CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf