Braking of high-speed flows in the magnetotail:THEMIS joint observations  

作　　者：Wensai Shang Zhonghua Yao Quanqi Shi Weijie Sun Suiyan Fu Jiang Liu Anmin Tian Qiugang Zong Zuyin Pu Ting Xiao Vassilis Angelopoulos 

机构地区：[1]Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment,School of Space Science and Physics,Shandong University [2]School of Earth and Space Sciences,Peking University [3]IGPP/ESS,University of California,Los Angeles Los Angeles

出　　处：《Chinese Science Bulletin》2014年第3期326-334,共9页

基　　金：supported by the National Natural Science Foundation of China(41031065,41074106,and 40974095);the Shandong Natural Science Foundation(JQ201112)

摘　　要：The motion and deceleration processes of plasma sheet high-speed flows have great significance to magnetospheric particle acceleration,magnetic field perturbation,magnetic flux transport,triggering of substorm,and the current system formation in the magnetotail.From February to April 2009,two satellites of the Time History of Events and Macroscale Interactions during Substorms mission,THA and THE,were often separated largely in Z direction,but had small X and Y separations.Such special configuration allows simultaneous observations of highspeed flows at the center and boundary of the plasma sheet.Based on selected case study and statistical analysis,it is found that for about 89%of the events we selected,the probe further away from the neutral sheet observed the high-speed flow earlier than the one close to the center,and the flow is mainly field aligned.And for about 95%events the probe further away from the neutral sheet observed higher X component of the plasma flow.With the hypothesis that parallel flow keeps the same speed during its earthward propagation while central plasma sheet stream uniformly or suddenly brakes on its way to the earth,we deduced the position where the deceleration begins to be between 13 Re and 17 Re downtail,where thenear-earth reconnection is supposed to occur.In addition,our statistical results show that dipolarization fronts observed in the central plasma sheet are more prominent than those observed in the plasma sheet boundary layer ahead of the high-speed flow.The motion and deceleration processes of plasma sheet high-speed flows have great significance to magnetospheric particle acceleration, magnetic field perturbation, magnetic flux transport, triggering of substorm, and the current system formation in the magnetotail. From February to April 2009, two satellites of the Time History of Events and Macroscale Interactions during Substorms mission, THA and THE, were often separated largely in Z direction, but had small X and Y separations. Such special configuration allows simultaneous observations of highspeed flows at the center and boundary of the plasma sheet. Based on selected case study and statistical analysis, it is found that for about 89 % of the events we selected, the probe further away from the neutral sheet observed the high-speed flow earlier than the one close to the center, and the flow is mainly field aligned. And for about 95 % events the probe further away from the neutral sheet observed higher X component of the plasma flow. With the hypothesis that parallel flow keeps the same speed during its earthward propagation while central plasma sheet stream uniformly or suddenly brakes on its way to the earth, we deduced the position where the deceleration begins to be between 13 Rc and 17 Re downtail, where the near-earth reconnection our statistical results observed in the central than those observed in ahead of the high-speed is supposed to occur. In addition, show that dipolarization fronts plasma sheet are more prominent the plasma sheet boundary layer flow.

关 键 词：高速制动 观测 等离子体片 磁流 减速过程 统计分析 边界层流 等离子体流 

分 类 号：P353[天文地球—空间物理学]