利用台灣日震觀測網的太陽影像資料研究 太陽差動自轉的變化情形;A Study of Solar Differential Rotation Based on Solar Images Obtained From Taiwan Oscillation Network

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题名:	利用台灣日震觀測網的太陽影像資料研究太陽差動自轉的變化情形;A Study of Solar Differential Rotation Based on Solar Images Obtained From Taiwan Oscillation Network
作者:	余秀珊;Hsiu-Shan Yu
贡献者:	太空科學研究所
关键词:	太陽差動自轉;日震學;solar differential rotation;helioseismology or solar seismology
日期:	2004-06-16
上传时间:	2009-09-22 09:46:39 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	太陽的差動自轉(solar differential rotation)可將原本南北方向的磁偶極場(poloidal field)拉成東西方向(toroidal field)。因此太陽差動自轉在太陽磁場的週期變化中，扮演著很重要的角色。早期科學家從追踨太陽黑子(sunspots)的運動所得到的太陽差動自轉模式受到太陽黑子分佈情形的限制，在時空解析度上，很難再進一步提升。台灣日震觀測網(Taiwan Oscillation Network, TON)提供一分鐘一張高時空解析度的broadband K-line image。這些K-line 影像圖中除了太陽黑子與明亮的譜斑(plages) 外還有超米粒組織的明亮邊界(supergranulation boundaries，SGB)，都可以作為研究太陽差動自轉的追蹤標記。由於超米粒組織的明亮邊界的緯度分佈甚廣且數量不受太陽週期的影響，因此藉著分析TON K-line image 可得高時空解析度之太陽表面差動自轉的情形。在本論文的研究中，我們從1994 年起，每年分析數日已經 remapped 的TON 資料來研究太陽差動自轉隨太陽週期的變化情形。初步的結果發現，在1994~2000 年間，太陽的轉速在北半球，有逐年減慢的趨勢，但在南半球，則是逐年的增快。但是進一步的檢驗 remapped 的資料後，發現有一部分的南北不對稱性是受到不正確的 remapped 影像的影響。因此本論文在太陽差動自轉隨太陽週期變化方面的研究仍未成功。但是在本研究中，我們設計了一種只要半天的資料量，就可以很快的求得太陽在不同緯度的自轉角速率。我們同時找到一種檢驗remapped 結果是否正確的方法。相信我們所研發的這兩項資料分析方法，將對未來利用TON 資料做日震分析的研究有很大的幫助。 i Solar latitudinal differential rotation, which can generate toroidal magnetic field from a poloidal magnetic field, plays an important role on solar dynamo and formation of solar cycle. Solar differential rotation was first found by tracing sunspots' motion. The well-known solar differential rotation formula obtained from sunspots' motion is only applicable to the middle- and lower- latitude regions and has a poor latitudinal resolution during solar minimum. Supergranulations, or chromosphere networks, or plages are excellent targets for studying solar differential rotation in all latitudes and during different phases of solar cycle. The one-minute broadband K-line images obtained from Taiwan Oscillation Network (TON) provide an opportunity to study differential rotation of supergranulations or plages up to very high latitude. Our preliminary results show that weak north-south asymmetry on solar differential rotation is found during years 1994~1997. Strong north-south asymmetry on solar differential rotation is found during years 1998~2000. According to our preliminary study, solar rotation rate decreases with time in northern hemisphere, but increases with time in southern hemisphere during years 1994~2000. However, further study indicates that the strong north-south asymmetry on solar differential rotation may partially due to incorrect mapping of the TON data sets we used in this thesis. Thus, our study of solar cycle dependence on solar differential rotation is not fully successful. But, in this thesis we have developed a very efficient way to obtain solar rotation rate at different latitude. We have also found a simple way to check and to improve the accuracy of a remapped image. Therefore, using the techniques developed in this thesis can provide accurate remapped images and real-time solar differential rotation information for future solar seismology study using TON data sets.
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