NDLI: Evolution and Flare Activity of $\delta$ -Sunspots in Cycle 23

Content Provider	Springer Nature Link
Author	Takizawa, K. Kitai, R.
Copyright Year	2015
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.
Starting Page	2093
Ending Page	2116
Page Count	24
File Format	PDF
ISSN	00380938
Journal	Solar Physics
Volume Number	290
Issue Number	7
e-ISSN	1573093X
Language	English
Publisher	Springer Netherlands
Publisher Date	2015-08-11
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Active regions Magnetic fields Photosphere Astrophysics and Astroparticles Atmospheric Sciences Extraterrestrial Physics, Space Sciences
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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