A distinct magnetic property of the inner penumbral boundary Formation of a stable umbra-penumbra boundary in a sunspot

Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F15%3A00449432" target="_blank" >RIV/67985815:_____/15:00449432 - isvavai.cz</a>
Result on the web
<a href="http://hdl.handle.net/11104/0250984" target="_blank" >http://hdl.handle.net/11104/0250984</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1051/0004-6361/201425501" target="_blank" >10.1051/0004-6361/201425501</a>

Result language
angličtina
Original language name
A distinct magnetic property of the inner penumbral boundary Formation of a stable umbra-penumbra boundary in a sunspot
Original language description
We study the evolving penumbra and the related changing value of the vertical component of the magnetic field (B-ver) on the boundary between umbra and penumbra using unique observations taken with GFPI/VTT. For comparison with stable sunspots, we also analyse the two maps observed by Hinode/SP on the same spot after the penumbra formed. The vertical component of the magnetic field, B-ver, at the umbra-penumbra boundary increases during penumbra formation owing to the incursion of the penumbra into umbral areas. After 2.5 h, the penumbra reaches a stable state as shown by the GFPI data. At this stable stage, the simultaneous Hinode/SP observations show a B-ver value comparable to that of umbra-penumbra boundaries of fully fledged sunspots (B-ver-stable). We confirm that the umbra-penumbra boundary, traditionally defined by an intensity threshold, is also characterised by a distinct canonical magnetic property, namely by B-ver-stable. During the penumbra formation process, the inner penumbra extends into regions where the umbra previously prevailed. Hence, in areas where B-ver is smaller than B-ver-stable, the magneto-convection mode operating in the umbra turns into a penumbral mode.
Czech name
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Czech description
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Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10308 - Astronomy (including astrophysics,space science)

Project
Result was created during the realization of more than one project. More information in the Projects tab.
Continuities
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year
2015
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

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