磁层顶通量传输事件轴向统计分析

Statistical Study of Axial Orientations of Flux Transfer Events at the Magnetopause

磁层顶通量传输事件(Flux Transfer Event,FTE)与磁重联相关,其典型特征为磁场法向分量的双极变化.在不同FTE模型里,FTE结构可能为重联的通量管、由多X线重联形成的闭合磁通量绳或者由单X线重联形成的开放磁场环,从而在磁层顶有不同的整体位形.使用一种新的轴向分析方法,对Cluster在一个向阳面磁层顶穿越季观测到的505个FTE进行统计研究.结果表明:在磁层顶中低纬度的侧翼,大多数FTE轴向均为沿磁层磁力线方向即南北方向,少数FTE轴向沿着不同于磁层磁力线方向的东西方向;在高纬磁层顶,大多数FTE轴向沿东西方向,少数FTE轴向沿着磁层磁力线方向即南北方向.这些统计特征有助于重新认识FTE的全球形态.

Flux Transfer Events （FTE） are related to magnetic reconnection. The typical charac- teristic of FTE is bipolar variation of the field component normal to the local magnetopause. There still exist different views about FTE global topology on the magnetopause. In different models, the FTE structures are either reconnected flux tubes, or magnetic flux ropes formed by multiple X-line reconnection or sheared magnetic loops formed by single X-line reconnection. To infer the global configuration of FTE, a statistical study of axial orientations of 505 FTE observed by Cluster during one dayside magnetopause crossing season is performed. The result shows that most FTE have north-south-orientated axes roughly aligned with the local magnetospheric flux tubes at both the low- and middle-latitude flanks. However, most FTE have dawn-dusk-orientated axes which are more consistent with the single or multiple X-line orientations at high latitude, especially near the cusp. These statistical features will improve our understanding about the global topology of FTE.