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Evolution and Flare Activity of \(\delta\)-Sunspots in Cycle 23

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Abstract

The emergence and magnetic evolution of solar active regions (ARs) of \(\beta\gamma\delta\)-type, which are known to be highly flare-productive, were studied with SOHO/MDI data in Cycle 23. We selected 31 ARs that can be observed from their birth phase as unbiased samples for our study. From the analysis of the magnetic topology (twist and writhe), we obtained the following results: i) Emerging \(\beta\gamma\delta\) ARs can be classified into three topological types as quasi-\(\beta\), writhed, and top-to-top. ii) Of these, the writhed and top-to-top types tend to show high flare activity. iii) As the signs of twist and writhe agree with each other in most cases of the writhed type (12 cases out of 13), we propose a magnetic model in which the emerging flux regions in a \(\beta\gamma\delta\) AR are not separated, but are united as a single structure below the solar surface. iv) Almost all the writhed-type ARs have downward knotted structures in the middle part of the magnetic flux tube. This is probably the essential property of \(\beta\gamma\delta\) ARs. v) The flare activity of \(\beta\gamma\delta\) ARs is highly correlated not only with the sunspot area, but also with the magnetic complexity. vi) We suggest that there is a possible scaling-law between the flare index and the maximum umbral area.

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Notes

  1. ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_REGIONS/USAF_MWL .

  2. http://solarscience.msfc.nasa.gov/greenwch.shtml .

  3. http://www.solarmonitor.org/ .

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Acknowledgements

The authors appreciate useful comments from an anonymous referee. We thank the SOHO, TRACE, and GOES consortia for their data. SOHO is an international cooperation between ESA and NASA. We are grateful to the staff of Kwasan and Hida observatories of Kyoto University for their continuing help. We wish to thank Hiroki Kurokawa and Yin Zhang for useful discussion. This work was supported by the Grant-in-Aid for the Global COE Program “The Next Generation of Physics, Spun from Universality and Emergence” from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. We are partially supported by the grant-in-aid from the Japanese MEXT (PI: R. Kitai No. 26400235).

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Authors and Affiliations

  1. Kwasan and Hida Observatories, Kyoto University, Yamashina-ku, Kyoto, 607-8417, Japan

    K. Takizawa & R. Kitai

  2. Bukkyo University, Kita-ku, Kyoto, 603-8301, Japan

    R. Kitai

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  1. K. Takizawa
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  2. R. Kitai
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Correspondence to K. Takizawa.

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Takizawa, K., Kitai, R. Evolution and Flare Activity of \(\delta\)-Sunspots in Cycle 23. Sol Phys 290, 2093–2116 (2015). https://doi.org/10.1007/s11207-015-0720-1

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  • DOI: https://doi.org/10.1007/s11207-015-0720-1

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