Statistical study of magnetotail flux ropes near the lunar orbit

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• 作者：SiQi Zhao ; AnMin Tian ; QuanQi Shi ; ChiJie Xiao…
• 关键词：magnetotail ; flux rope ; TCR ; dawn ; dusk asymmetry ; reconnection site
• 刊名：SCIENCE CHINA Technological Sciences
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：59
• 期：10
• 页码：1591-1596
• 全文大小：1,100 KB
• 刊物类别：Engineering
• 刊物主题：Chinese Library of Science
  Engineering, general
  
• 出版者：Science China Press, co-published with Springer
• ISSN：1869-1900
• 卷排序：59

文摘

Flux-rope/TCR events near the magnetotail lunar orbit (−67R_E < GSM X* < −39R_E) were studied using magnetic-field and plasma data measured by THEMIS B and C between January 2011 and March 2012. The aberrant coordinate GSM*, where the X* axis is rotated 4° relative to GSM-X, was used to count the occurrence rate. The number ratio of earthward to tailward events was about 3:5. Moreover, the event occurrence rate distribution showed a clear dawn-dusk asymmetry distribution, with dusk-side events accounting for 57.98%. A superposed epoch analysis of the flux-rope events showed that earthward events had a shorter duration in the leading than in the trailing part. Earthward events also displayed a lower temperature and a lower flow speed than tailward events. We studied the relationship between the event occurrence rate and geomagnetic activity level even further. The occurrence rate of tailward flux-rope/TCR events increases with increasing AE-index, whereas earthward events occur mainly in the relatively quiet period of geomagnetic activity (AE ∼ 100–00 nT). Flux-rope/TCR events identified within a 10 mm time frame were treated as belonging to a single reconnection event. By comparing the occurrence rates of earthward and tailward events along X*, we estimated the most likely location of the near-Earth reconnection site as X* = −36R_E.