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0004-637X_796_2_77.pdf | 2.13 MB | Adobe PDF | 見る/開く |
タイトル: | FORMATION AND DECAY OF RUDIMENTARY PENUMBRA AROUND A PORE |
著者: | Watanabe, Hiroko Kitai, Reizaburo Otsuji, Kenichi |
著者名の別形: | 渡邉, 皓子 |
キーワード: | magnetic fields - Sun photosphere - sunspots |
発行日: | 1-Dec-2014 |
出版者: | American Astronomical Society |
誌名: | The Astrophysical Journal |
巻: | 796 |
号: | 2 |
論文番号: | 77 |
抄録: | We analyze the evolution of a pore in the active region NOAA 10940 using the data obtained by the Hinode satellite on 2007 February 3. The pore we analyzed showed the formation of a rudimentary penumbra structure, succeeded by an abrupt disappearance after about 5 hr. The pore had an approximate radius of 3.5 Mm and a total magnetic flux of 3.0 × 10[19] Mx, which is a little smaller than the necessary magnetic flux for penumbral formation supposed by Rucklidge et al. (1-1.5 × 10[20] Mx). Our observation describes a rare phenomenon which was in the unstable phase between a pore and a sunspot. The area of the dark umbra gradually decreased when the rudimentary penumbral filaments formed the penumbral structure, meaning that the penumbra develops at the expense of the umbral magnetic flux. This statement was confirmed by a rough estimation of the magnetic flux variation observed by the Hinode Fe I magnetogram. Five hours after the formation phase, the decay phase began. In this decaying phase, multiple opposite polarity patches are found to appear in the exterior of the pore (a different location from the penumbra formation site). We interpret these opposite polarities as signatures of the horizontal magnetic field, which preferably appears in the course of the unstable reconfiguration of the magnetic field structure. During the course of the disappearance of the penumbra, the horizontal penumbral field seems to become vertical because of the dark umbral area that recovered by about 10%. |
著作権等: | ©2014. The American Astronomical Society. |
URI: | http://hdl.handle.net/2433/192763 |
DOI(出版社版): | 10.1088/0004-637X/796/2/77 |
出現コレクション: | 学術雑誌掲載論文等 |
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