Prominent Photospheric Downflows on Magnetic Neutral Line in a Delta-Type Sunspot |
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Authors: | K Takizawa R Kitai Y Zhang |
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Institution: | 1. Kwasan and Hida Observatories, Kyoto University, Yamashina-ku, Kyoto, 607-8471, Japan 2. National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, China
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Abstract: | It is known that ??-type sunspot groups have a high flare productivity and produce strong flares. In particular, ?|?? type sunspots are the most active type of all. A ?|?? active region NOAA?9957 with frequent flux cancellations but without any marked flare activity during its decay phase was studied in this work. Using SOHO/MDI Dopplergrams and magnetograms, we detected continuous prominent downflow motions of 1500??C?1700?m?s?1 for several hours on the magnetic neutral line in this region. In the downflow region, penumbral structures were observed to decay. We will interpret and discuss the phenomenon as a case of submergence of the magnetic flux. |
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