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The magnetic nature of umbra-penumbra boundary in sunspots
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SYSNO ASEP 0495019 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title The magnetic nature of umbra-penumbra boundary in sunspots Author(s) Jurčák, Jan (ASU-R) RID, ORCID
Rezaei, R. (DE)
Bello González, N. (ES)
Schlichenmaier, R. (DE)
Vomlel, Jiří (UTIA-B) RID, ORCIDArticle number L4 Source Title Astronomy & Astrophysics. - : EDP Sciences - ISSN 0004-6361
Roč. 611, March (2018)Number of pages 13 s. Publication form Online - E Language eng - English Country FR - France Keywords Sun ; magnetic fields ; photosphere Subject RIV BN - Astronomy, Celestial Mechanics, Astrophysics OECD category Astronomy (including astrophysics,space science) Subject RIV - cooperation Institute of Information Theory and Automation - Computer Applications, Robotics Institutional support ASU-R - RVO:67985815 ; UTIA-B - RVO:67985556 UT WOS 000428422500001 EID SCOPUS 85044724208 DOI 10.1051/0004-6361/201732528 Annotation We aim at studying the magnetic nature of umbra-penumbra boundaries in sunspots of different sizes, morphologies, evolutionary stages, and phases of the solar cycle. We statistically prove that the umbra-penumbra boundary in stable sunspots is characterised by an invariant value of the vertical magnetic field component: the vertical component of the magnetic field strength does not depend on the umbra size, its morphology, and phase of the solar cycle. With the statistical Bayesian inference, we find that the strength of the vertical magnetic field component is, with a likelihood of 99%, in the range of 1849-1885 G with the most probable value of 1867 G. In contrast, the magnetic field strength and inclination averaged along individual boundaries are found to be dependent on the umbral size: the larger the umbra, the stronger and more horizontal the magnetic field at its boundary. Workplace Astronomical Institute Contact Radka Svašková, bibl@asu.cas.cz, Tel.: 323 620 326 Year of Publishing 2019
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