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Fan-shaped jets above the light bridge of a sunspot driven by reconnection
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
Number of Authors: 42016 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 590, article id A57Article in journal (Refereed) Published
Abstract [en]

We report on a fan-shaped set of high-speed jets above a strongly magnetized light bridge (LB) of a sunspot observed in the H alpha line. We study the origin, dynamics, and thermal properties of the jets using high-resolution imaging spectroscopy in H alpha from the Swedish 1m Solar Telescope and data from the Solar Dynamics Observatory and Hinode. The H alpha jets have lengths of 7-38 Mm, are impulsively accelerated to a speed of similar to 100 km s(-1) close to photospheric footpoints in the LB, and exhibit a constant deceleration consistent with solar effective gravity. They are predominantly launched from one edge of the light bridge, and their footpoints appear bright in the H alpha wings. Atmospheric Imaging Assembly data indicates elongated brightenings that are nearly co-spatial with the H alpha jets. We interpret them as jets of transition region temperatures. The magnetic field in the light bridge has a strength of 0.8-2 kG and it is nearly horizontal. All jet properties are consistent with magnetic reconnection as the driver.

Place, publisher, year, edition, pages
2016. Vol. 590, article id A57
Keywords [en]
techniques: imaging spectroscopy, Sun: chromosphere, Sun: photosphere, sunspots
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-132496DOI: 10.1051/0004-6361/201528022ISI: 000378106800086OAI: oai:DiVA.org:su-132496DiVA, id: diva2:953207
Available from: 2016-08-17 Created: 2016-08-15 Last updated: 2018-06-21Bibliographically approved
In thesis
1.
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2. The dynamic chromosphere: Results and techniques with an observational approach
Open this publication in new window or tab >>The dynamic chromosphere: Results and techniques with an observational approach
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The chromosphere is a critical interface between the relatively cold photosphere and the hot corona. Its landscape is rich in very dynamic phenomena such as jets, spicules, and surges, which are thought to play an important role in the heating of the Sun’s upper atmosphere. However, these events are often driven by mechanisms that are not entirely understood owing to the complex physical conditions governing the chromosphere. In the average chromosphere, the magnetic pressure often dominates over the gas pressure. Thus the structure and dynamics of this layer are mainly regulated by the magnetic field configuration.

This thesis is based on three projects that investigate some chromospheric dynamic phenomena and their relation with the magnetic field. In these projects, we follow an experimental approach, by analysing high-resolution ground-based observations with spectropolarimetry as well as satellite co-observations.

The first project focuses on exotic fan-shaped jets that are sometimes observed above sunspot light bridges. We investigate the thermal properties and the dynamics of these jets, and suggest magnetic reconnection as the mechanism producing these events.

In the second project, we study a δ-sunspot penumbra that harbours fan-shaped jets. By using inversion techniques, we retrieve the 3D structure of the magnetic field and temperature, which reveal that the magnetic reconnection driving the fan-shaped jets occurs in the lower chromosphere.

In the third project, we investigate the role of the magnetic field in a unipolar supergranular network cell having a radial arrangement of the fibrils. For this chromospheric structure, we suggest a model of the magnetic topology based on multiwavelength observations and inversion techniques.

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University, 2018. p. 68
Keywords
Sun, chromosphere, jets, sunspots, imaging, spectropolarimetry
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-157343 (URN)978-91-7797-342-3 (ISBN)978-91-7797-343-0 (ISBN)
Public defence
2018-09-07, sal FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.

Available from: 2018-08-15 Created: 2018-06-19 Last updated: 2018-08-14Bibliographically approved

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