磁尾爆发性整体流与亚暴的关系

Relation of bursty bulk flows in the magnetotail and substorms

利用星簇Cluster的三颗卫星(C1,C3和C4)在2001年和2002年的数据,研究磁尾爆发性整体流(BBF,Bursty Bulk Flow)事件及其与亚暴的关系.三颗卫星可以同时观测到同一次BBF事件,有时只有一颗或两颗观测到BBF,其原因有:(1)等离子体整体流的速度峰值满足BBF选取原则中的峰值要求,但卫星的运行轨道不满足;(2)卫星处于所要求的区域内,等离子体整体流的速度峰值不满足;(3)中性片的复杂结构及其运动使得选取条件不能同时满足;(4)BBF空间分布高度局域化.统计研究结果表明:单颗卫星观测存在局限性,C1、C3和C4卫星独立观测到BBF的持续总时间分别占它们联合观测到的55.07%、77.48%和55.52%;大部分亚暴爆发期间都能观测到BBF,甚至在一次亚暴爆发期间观测到多次BBF;少数亚暴爆发期间没有观测到BBF.

By using the data of three satellites of Cluster from 2001 to 2002, we study BBF in the magnetotail and its relationship to substorm. One or two of three satellites have already observed the BBF, but the rest haven＇t sometimes. When the peak value of bulk velocity satisfies condition requested in the selection nile, the satellite isn＇t in the region requested in the nile. When the satellite is in the requested region, the peak value of bulk velocity doesn＇t satisfy. Due to the complicated structure and motion of the neutral sheet, all the rules can＇t be satisfied simultaneously. Since BBF is high localized, it is very difficult to be observed. From the point of statistical view, there are some limiting factors in the results obtained by one single satellite. The whole duration of BBF observed by C1, C3, C4 account for 55.07, 77.48, and 55.52 percents of that observed by three satellites jointly. Statistical studies indicate that most substorms are accompanied by one or more BBF events. Only a few substorms are not accompanied by BBF events. The main reasons are as follows. The orbit of satellite isn＇t in the region requested in the selection nile. The structure and motion of neutral sheet are complicated. The BBF selection criteria are limited. BBF events are high localized.