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CRISP spectropolarimetric imaging of penumbral fine structure
Stockholm University, Faculty of Science, Department of Astronomy. (Kungl. Vetenskapsakademiens inst. f. solfysik)
Stockholm University, Faculty of Science, Department of Astronomy. (Kungl. Vetenskapsakademiens inst. f. solfysik)
Stockholm University, Faculty of Science, Department of Astronomy. (Kungl. Vetenskapsakademiens inst. f. solfysik)
Stockholm University, Faculty of Science, Department of Astronomy. (Kungl. Vetenskapsakademiens inst. f. solfysik)
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2008 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 689, no 1, L69- p.Article in journal (Refereed) Published
Abstract [en]

We discuss penumbral fine structure in a small part of a pore, observed with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope (SST), close to its diffraction limit of 0.16 . Milne-Eddington inversions applied to these Stokes data reveal large variations of field strength and inclination angle over dark-cored penumbral intrusions and a dark-cored light bridge. The mid-outer part of this penumbra structure shows 0.3 wide spines, separated by 1.6 (1200 km) and associated with 30° inclination variations. Between these spines, there are no small-scale magnetic structures that easily can be identified with individual flux tubes. A structure with nearly 10° more vertical and weaker magnetic field is seen midway between two spines. This structure is cospatial with the brightest penumbral filament, possibly indicating the location of a convective upflow from below.

Place, publisher, year, edition, pages
2008. Vol. 689, no 1, L69- p.
Keyword [en]
sunspot, polarimetry, sun, spectropolarimetry
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:su:diva-16337DOI: 10.1086/595744ISI: 000262733800018OAI: oai:DiVA.org:su-16337DiVA: diva2:182857
Available from: 2008-12-17 Created: 2008-12-17 Last updated: 2011-02-11Bibliographically approved
In thesis
1. Imaging spectropolarimetry of solar active regions
Open this publication in new window or tab >>Imaging spectropolarimetry of solar active regions
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Solar magnetic fields span a wide range of spatial scales from sunspots and plages to magnetic bright points. A clear understanding of the physical processes underlying the evolution of these magnetic features requires high-resolution spectropolarimetric observations of solar active regions and comparisons with synthetic data from simulations. This thesis is based on observations with the Swedish 1-m Solar Telescope (SST) and the CRISP imaging spectropolarimeter which, processed with a sophisticated image restoration technique, produce data of unsurpassed quality. The Fe I 630.25 nm line is used for all the spectropolarimetric observations.

It appears likely that present telescopes resolve the fundamental scales of penumbral filaments. However, the penumbrae of sunspots are still not fully understood, with various theoretical models competing to explain their fine structure and flows. We analyze spectropolarimetric observations with a resolution close to the SST diffraction limit of 0.16 arcsecond. Using inversion techniques, we map the line-of-sight velocities and the magnetic-field configuration of dark-cored penumbral filaments.

Over the past decade, sunspots and quiet sun magnetic fields have received considerable attention, with intermediate plage regions being somewhat neglected. We perform a detailed analysis of a plage region and present the first observational evidence of a small-scale granular magneto-convection pattern associated with a plage region.

Magnetic bright points are believed to be formed due to magnetic field intensification caused by flux-tube collapse involving strong downflows. Although magneto-hydrodynamic (MHD) simulations agree with this view, only a few observations with adequate spatial resolution exist in support of the simulations. We present several cases of bright-point formation associated with strong downflows, which qualitatively agree with simulations and past observations. However, we find the field intensification to be transient rather than permanent.

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University, 2011. 51 p.
Keyword
Sun, Spectropolarimetry, Solar magnetic fields, Sunspots, Plages
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-54687 (URN)978-91-7447-212-7 (ISBN)
Public defence
2011-03-16, FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:15 (English)
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Note
At the time of the doctoral defense, the following paper was unpublished: Paper 3: Accepted.Available from: 2011-02-22 Created: 2011-02-11 Last updated: 2011-02-22Bibliographically approved

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Scharmer, Göran B.Narayan, GautamHillberg, Tomasde la Cruz Rodriguez, JaimeLöfdahl, Mats G.Kiselman, Danvan Noort, Michiel
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