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The chromosphere above a delta-sunspot in the presence of fan-shaped jets
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.ORCID iD: 0000-0002-4640-5658
Number of Authors: 32018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 609, article id A14Article in journal (Refereed) Published
Abstract [en]

Context. Delta-sunspots are known to be favourable locations for fast and energetic events like flares and coronal mass ejections. The photosphere of this sunspot type has been thoroughly investigated in the past three decades. The atmospheric conditions in the chromosphere are not as well known, however. Aims. This study is focused on the chromosphere of a delta-sunspot that harbours a series of fan-shaped jets in its penumbra. The aim of this study is to establish the magnetic field topology and the temperature distribution in the presence of jets in the photosphere and the chromosphere. Methods. We use data from the Swedish 1m Solar Telescope (SST) and the Solar Dynamics Observatory. We invert the spectropolarimetric Fe I 6302 angstrom and Ca II 8542 angstrom data from the SST using the non-LTE inversion code NICOLE to estimate the magnetic field configuration, temperature, and velocity structure in the chromosphere. Results. A loop-like magnetic structure is observed to emerge in the penumbra of the sunspot. The jets are launched from this structure. Magnetic reconnection between this emerging field and the pre-existing vertical field is suggested by hot plasma patches on the interface between the two fields. The height at which the reconnection takes place is located between log tau(500) = 2 and log tau(500) = -3. The magnetic field vector and the atmospheric temperature maps show a stationary configuration during the whole observation.

Place, publisher, year, edition, pages
2018. Vol. 609, article id A14
Keywords [en]
Sun: chromosphere, Sun: photosphere, sunspots, techniques: polarimetric
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-152486DOI: 10.1051/0004-6361/201731504ISI: 000418963900014OAI: oai:DiVA.org:su-152486DiVA, id: diva2:1181324
Available from: 2018-02-08 Created: 2018-02-08 Last updated: 2018-06-21Bibliographically approved
In thesis
1. 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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