兩類快速電漿流事件與夜側極光活動關係之研究; A Study of Relationships between Two Groups of Fast Flow Events and Nightside Auroral Activities

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Title:	兩類快速電漿流事件與夜側極光活動關係之研究;A Study of Relationships between Two Groups of Fast Flow Events and Nightside Auroral Activities
Authors:	謝旻秀;Min-shiu Hsieh
Contributors:	太空科學研究所
Keywords:	極光;快速電漿流;aurora;fast plasma flows
Date:	2008-06-03
Issue Date:	2009-09-22 09:48:51 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	在這篇論文中，我們將探討磁尾電漿片中存在短暫的快速電漿流現象與高緯地區夜側極光活動之間的關聯。我們使用了1997到1998兩年間的Geotail衛星資料，將電漿流速度分為平行與垂直背景磁場兩個部份，並採用其分別投影在日地連線方向的分量大小為快速電漿流選取的依據，即Vpara,x和Vper,x。此外，我們同樣使用了這兩年間Polar衛星在極區上空所拍攝到的全球極光影像資料，量化計算在每一個快速電漿流事件中，相對應的夜側極光功率隨時間的變化。我們將所有快速電漿流事件分為兩類，第一類是在選取的30分鐘事件內，同樣有大於300 km/s的Vpara,x和Vper,x快速電漿流出現，第二類則是只有快速Vpara,x而沒有快速Vper,x電漿流出現的事件。我們的統計結果發現，第一類快速電漿流事件與整體夜側極光活動增強的正相關性比第二類來的高，而幾乎所有的第二類快速電漿流事件都和整體夜側極光活動的增強無正相關性。另一方面，我們也發現到幾乎所有的第二類快速電漿流事件，都發生在整體夜側極光活動逐漸減弱或是寧靜期時。 In this study, we investigate relationships between nightside auroral activities and fast flow events occurred in the plasma sheet during the period of 1997 and 1998. We first identify fast flows using a criterion of Vpara,x > 300 km/s and Vper,x > 300km/s, where Vpara,x(Vper,x) is the X component of the ion velocity parallel (perpendicular) to the ambient magnetic field. We then quantitatively estimate a rate of change of auroral power over polar region using Polar Ultraviolet Imager auroral images for each event. We divide all the fast flow events into two groups. GroupΙ(Π) is a group of the parallel fast flow events associated with (without) the occurrence of perpendicular fast flows in the period of 30 min. It is found that Group Ι fast flow events have a better relationship with the enhancing nightside auroral power than Group Π, and almost all the Group Π fast flow events occur during the periods of relatively constant or decreasing nightside auroral power.
Appears in Collections:	[Graduate Institute of Space Science] Department of Earth Sciences

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