Observations of multiple X-line structure in the Earth's magnetotail current sheet: A Cluster case study

Observations of the Earth's magnetotail made by the four Cluster spacecraft on October 2 2003 are presented. Multi-spacecraft analysis is used to show that the variations in field and flow observed in the vicinity of the magnetotail current sheet are most consistent with a series of two active reconnection sites bounding an Earthward moving flux rope. We demonstrate that a single spacecraft analysis of the same data leads to the incorrect conclusion that a single X-line is moving tailward. The implications of this in relation to the interpretation of single spacecraft observations are outlined. These results show that reconnection can occur simultaneously at different points in the near-Earth magnetotail current sheet, providing ( further) important experimental validation of multiple X - line reconnection theories on the mesoscale ( tens of ion inertial length) level.