典型文献
Chinese Sunspot Drawings and Their Digitization—(VII) Sunspot Penumbra to Umbra Area Ratio Using the Hand-Drawing Records from Yunnan Observatories
文献摘要：
The ratio of penumbral to umbra area of sunspots plays a crucial role in the solar physics fields, especially for understanding the origin and evolution of the solar activity cycle. By analyzing the recently digitized sunspot drawings observed from Yunnan Observatories (1957–2021), we investigate the long-term variation of the penumbral to umbra area ratio of sunspots. An automatic extraction method, based on the maximum between-class variance and the morphological discrimination, is used to accurately extract penumbra and umbra and to calculate the ratio over six solar cycles (cycle 19–24). The expected value of the ratio of penumbra to umbra area is found to be 6.63 ± 0.98, and it does not exhibit any systematic variation with sunspot latitudes and phases. The average ratio fluctuates from 5 to 7.5 per year and the overall trend has decreased after 1999 compared to the previous one. The ratio of sunspot penumbra to umbra area satisfies the log-normal distribution, implying that its variation is related to the evolution of the photospheric magnetic field. Our results are consistent with previous works.
文献关键词：
中图分类号：
作者姓名：
Jia-Wei Hou;Shu-Guang Zeng;Sheng Zheng;Xiao-Yu Luo;Lin-Hua Deng;Yang-Yang Li;Yan-Qing Chen;Gang-Hua Lin;Yong-Li Feng;Jin-Ping Tao
作者机构：
Center for Astronomy and Space Sciences,China Three Gorges University,Yichang 443002,China;College of Science,China Three Gorges University,Yichang 443002,China;Yunnan Observatories,Chinese Academy of Sciences,Kunming 650216,China;National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China
文献出处：
引用格式：
[1]Jia-Wei Hou;Shu-Guang Zeng;Sheng Zheng;Xiao-Yu Luo;Lin-Hua Deng;Yang-Yang Li;Yan-Qing Chen;Gang-Hua Lin;Yong-Li Feng;Jin-Ping Tao-.Chinese Sunspot Drawings and Their Digitization—(VII) Sunspot Penumbra to Umbra Area Ratio Using the Hand-Drawing Records from Yunnan Observatories)[J].天文和天体物理学研究,2022(09):132-139
A类：
Sunspot,Drawings,Digitization,Umbra,Observatories,penumbral,umbra,sunspots,photospheric
B类：
Chinese,Their,VII,Penumbra,Area,Ratio,Using,Hand,Records,from,Yunnan,ratio,area,plays,crucial,role,solar,physics,fields,especially,understanding,origin,evolution,activity,By,analyzing,recently,digitized,drawings,observed,investigate,long,term,variation,An,automatic,extraction,method,maximum,between,class,variance,morphological,discrimination,used,accurately,calculate,six,cycles,expected,value,found,does,not,exhibit,any,systematic,latitudes,phases,average,fluctuates,per,year,overall,trend,decreased,after,compared,previous,one,satisfies,normal,distribution,implying,that,its,related,magnetic,Our,results,consistent,works
AB值：
0.448827
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