中磁尾重联触发亚暴的单事例分析

Mid-tail magnetic reconnection triggering substorm:A case study

磁层亚暴的发生与近磁尾(约6～8 R_E)电流片中断和中磁尾(约20～30 R_E)磁场重联密切相关,而极光的极向扩展、电流片中断和磁尾重联的时序过程对于认识亚暴的触发机制至关重要.本文利用位于中磁尾的CLUSTER卫星,同步轨道附近LANL-01、LANL-97卫星,近磁尾POLAR和极区IMAGE卫星的观测,分析了单个亚暴事例.结果表明,在此事件中,中磁尾磁场重联起始比近尾电流片中断早3 min发生,电流片中断发生4 min后,IMAGE卫星观测到极光增亮,同时AE指数突然增大,亚暴膨胀相起始.观测结果与亚暴中性线模型较为吻合.

Onset of a substorm is closely correlated with the current disruption in the near-Earth magnetotail, about 6~8 RE and magnetic reconnection in the middle magnetotail, around 20 ~ 30 RE. It is vital to understand the onset of a substorm by studying the time series among polar expansion of aurora, current disruption and magnetic reconnection. In this paper, with measurements from the Cluster spacecraft in the middle magnetotail, LANL-01 and LANL-97 at the synchronous orbit, POLAR in the near-earth magnetotail and IMAGE at polar region, a single substorm event is presented. The analysis indicates that magnetic reconnection is 3 minutes earlier than the current disruption in the near-earth magnetotail. Aurora brightening is observed by IMAGE 4 minutes after the current disruption. Simultaneously, the sharply increment of the AE index implies the substorm onset. The observational result is consistent with the Near Earth Neutral Line model （NENL）.