2004年2月11日Cluster卫星和CUTLASS雷达同时观测的磁通量传输事件

本文分析了2004年2月11日11:00～11:40 UT期间Cluster卫星簇的磁通门磁力计FGM）、等离子体电子及电流试验仪（PEACE）和CUTLASS 芬兰雷达对多个磁通量传输事件(FTEs)的同时观测. 在此期间，Cluster卫星簇位于北半球外极隙区附近，并于11:18 UT左右穿出磁层顶进入磁鞘，四颗卫星同时观测到了多个FTEs, 其出现具有准周期性，周期约为130 s. 利用Cluster四颗卫星的多点同时观测数据，采用最小方向微分法和时空微分方法，我们推断这些FTEs是尺度大小约为(0.87～1.81)R_E的准二维结构，其运动方向为东北方向，与Cooling模型预测方向基本一致. CUTLASS芬兰雷达在相应的电离层区域观测到了明显的“极向运动雷达极光”结构，这些结构与Cluster卫星簇观测的FTEs有着很好的对应关系，它们是FTEs的雷达观测特征.

Simultaneous Cluster and CUTLASS observations of FTEs on 11 February 2004

This paper analyzed the observations of the FGM and PEACE on Cluster spacecraft, and the CUTLASS Finland radar between 11:00 and 11:40 UTon 11 February 2004 In this interval, the Cluster spacecraft array was encountering the northern hemisphere, high altitude cusp, and crossing the magnetopause into the magnetosheath at about 11:18 UT. A large number of flux transfer events (FTEs) were observed by all 4 Cluster spacecraft. It is found that these FTEs appeared quasi periodically with a period of about 130 s. Since all 4 Cluster spacecraft observed these FTEs, we applied the four spacecraft techniques “Minimum Directional Derivative (or Difference)" (MDD) and “Spatio temporal Difference" (STD) to calculate the dimension, motion and scale of these FTEs. The inferred northwardly reconnected flux tubes for these FTEs are shown to move northward or north east and tailward with a quasi-2-D structure and a scale of (0.87～1.81) R_E. The ionospheric footprint of the Cluster spacecraft during the boundary passage is shown to map centrally within the field-of-view of the CUTLASS Finland radar. It is shown that the backscatter power of CUTLASS data enhanced in synchrony with the magnetospheric FTEs at the latitude of the Cluster footprint. These radar auroral features subsequently propagated poleward, forming classic “poleward-moving radar auroral form" structures at higher latitudes. Whilst, the FTE motions are shown to be consistent with the expected motion of reconnected magnetic flux tubes over the surface of the magnetopause, arising from a predominantly sub solar reconnection site during the prevailing upstream conditions.