日冕洞演化與高速太陽風之關係;Evolution of Coronal Hole and the Relationship with High-Speed Solar Wind

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题名:	日冕洞演化與高速太陽風之關係;Evolution of Coronal Hole and the Relationship with High-Speed Solar Wind
作者:	廖啓舜;Liao, Chi-Shun
贡献者:	太空科學與工程研究所
关键词:	日冕洞;演化;高速太陽風;太陽週期;長生命週期
日期:	2023-07-25
上传时间:	2024-09-19 14:48:52 (UTC+8)
出版者:	國立中央大學
摘要:	本篇論文使用SDO/AIA 193 Å太陽影像、SDO/HMI磁場圖，以及OMNI資料庫在1 AU處的太陽風資料，分析2010年6月至2021年1月之間的181個中低緯度日冕洞的特徵，包含日冕洞對近地太陽風的影響程度 (計算結果類似日冕洞面積，但概念不同，以下簡稱ICH-HSS)、位置、磁場強度、磁通量等，並探討其與太陽風速率的相關性。我們的研究內容主要分為日冕洞事件的特性分析與長生命週期的演化，特性分析的結果顯示，在分析時間內的日冕洞事件中，ICH-HSS與太陽風速率呈正相關 (相關係數r = 0.53-0.57)；日冕洞磁通量與太陽風速率呈相關 (r = 0.41-0.45)；ICH-HSS與磁場強度雖然呈正相關但並不顯著 (r = 0.25-0.45)；日冕洞磁場強度與太陽風速率則不相關 (r < 0.25)。另外，在長達10年的分析期間內，日冕洞磁場強度與磁通量的變化趨勢與太陽黑子數一致；ICH-HSS有著相同的變化趨勢，但時間上較太陽黑子數延遲1-2年；太陽風速率則沒有與太陽黑子數相同的變化趨勢，但從中我們可以觀察到長生命週期的日冕洞。針對長生命週期的日冕洞，我們共發現7個被重複觀測達5次以上的日冕洞，其ICH-HSS與Heinemann et al. (2018a) 中日冕洞面積的演化過程有相似的發現，其中6個事件有著成長期、極大期，及衰退期，且每個日冕洞的演化過程不一。除了ICH-HSS有明顯的演化過程，我們也發現磁場強度、磁通量、以及太陽風速率也隨著演化過程而呈現與ICH-HSS相似的趨勢。在本論文的研究中，在181個事件中有59個事件找不到相對應的太陽風速率。這可能是日冕物質拋射 (Coronal Mass Ejection，CME)、行星際空間的環境等原因，導致這個結果，我們會另外針對這些事件討論。 ;This thesis analyzes the characteristics of 181 low to mid-latitude coronal holes between June 2010 and January 2021 using SDO/AIA 193 Å solar image, SDO/HMI magnetogram, and OMNI database (solar wind data at 1 AU). The analyzed features include the impact of coronal hole on high-speed streams (ICH-HSS), which represents the influence of coronal hole on the near-Earth solar wind. It is calculated based on the coronal hole area and the weighting in the spatial distribution function. Additionally, the study examines the position, magnetic field strength, magnetic flux, and their correlations with solar wind speed. The research is divided into two main parts: the analysis of coronal hole events′ characteristics and the investigation of long-lived events′ evolution. The analysis of event characteristics reveals a positive correlation between ICH-HSS and solar wind speed (correlation coefficient r = 0.53-0.57). Furthermore, the coronal hole magnetic flux shows a correlation with solar wind speed (r = 0.41-0.45), while the correlation between ICH-HSS and magnetic field strength is positive but not significant (r = 0.25-0.45). The magnetic field strength of coronal holes is found to be unrelated to solar wind speed (r < 0.25). Over the 10-year analysis period, the variation trend of magnetic field strength and magnetic flux in coronal holes is consistent with those of sunspot numbers. ICH-HSS exhibits a similar trend but with a delay of 1-2 years compared to sunspot numbers. On the other hand, solar wind speed does not display the same variation trend as sunspot numbers. However, the study reveals the presence of long-lived coronal holes. Seven coronal holes that were observed at least 5 times during the study period dentified. The evolution of ICH-HSS in these long-lived events corresponds to the findings reported by Heinemann et al. (2018a) regarding the evolution of coronal hole area. Each coronal hole exhibits a growing phase, a maximum phase, and a decaying phase, but the evolution process varies case by case. In addition to the evident evolution of ICH-HSS, the magnetic field strength, magnetic flux, and solar wind speed also demonstrate similar trends throughout the evolution process. In this study, 59 events were found lacking corresponding solar wind speed data among 181 analyzed events. This discrepancy may be attributed to factors such as coronal mass ejections (CMEs) and the interplanetary space environment. Further discussions will be conducted to address these specific events.
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