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  Study of Sunspot Penumbra to Umbra Area Ratio Using Kodaikanal White-light Digitised Data

Jha, B. K., Mandal, S., & Banerjee, D. (2019). Study of Sunspot Penumbra to Umbra Area Ratio Using Kodaikanal White-light Digitised Data. Solar Physics, 294(6): 72. doi:10.1007/s11207-019-1462-2.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0006-67E0-9 Version Permalink: http://hdl.handle.net/21.11116/0000-0006-67E1-8
Genre: Journal Article

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 Creators:
Jha, Bibhuti Kumar, Author
Mandal, Sudip1, Author
Banerjee, Dipankar, Author
Affiliations:
1Max Planck Institute for Solar System Research, Max Planck Society, Justus-von-Liebig-Weg 3, 37077 Göttingen, DE, ou_1125546              

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 Abstract: We study the long-term behaviour of the sunspot penumbra to umbra area ratio by analysing recently digitised Kodaikanal white-light data (1923 – 2011). We implement an automatic umbra extraction method and compute the ratio over eight solar cycles (Cycles 16 – 23). Although the average ratio does not show any variation with spot latitudes, cycle phases and strengths, it increases from 5.5 to 6 as the sunspot size increases from 100 μhem to 2000 μhem. Interestingly, our analysis also reveals that this ratio for smaller sunspots (area <100 μhem) does not have any long-term systematic trend as was earlier reported from the photographic results of the Royal Observatory, Greenwich (RGO). To verify the same, we apply our automated extraction technique to Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI) continuum images (1996 – 2010). Results from this data not only confirm our previous findings, but they also show the robustness of our analysis method.

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Language(s): eng - English
 Dates: 2019
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Method: Peer
 Identifiers: DOI: 10.1007/s11207-019-1462-2
 Degree: -

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Title: Solar Physics
  Other : Sol. Phys.
Source Genre: Journal
 Creator(s):
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Publ. Info: Dordrecht, Holland : Kluwer, etc.
Pages: - Volume / Issue: 294 (6) Sequence Number: 72 Start / End Page: - Identifier: ISSN: 0038-0938
CoNE: https://pure.mpg.de/cone/journals/resource/954925445694