Chinese Sunspot Drawings and Their Digitization—(Ⅶ) Sunspot Penumbra to Umbra Area Ratio Using the Hand-Drawing Records from Yunnan Observatories  

作　　者：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 

机构地区：[1]Center for Astronomy and Space Sciences,China Three Gorges University,Yichang 443002,China [2]College of Science,China Three Gorges University,Yichang 43002,China [3]Yunnan Observatories,Chinese Academy of Sciences,Kunming.650216,China [4]National Astronomical Observatories,Chinese Academy of Sciences,Kunming,650216,China

出　　处：《Research in Astronomy and Astrophysics》2022年第9期132-139,共8页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. U2031202 and U1731124);the special foundation work of the Ministry of Science and Technology of China (Grant No. 2014FY120300);the 13th Five-year Informatization Plan of Chinese Academy of Sciences (Grant No. XXH13505-04)。

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.

关 键 词：Sun:sunspots Sun:photosphere Sun:activity techniques:image processing 

分 类 号：P182.41[天文地球—天文学]