Global Topology, Motion, and Convection of a Northward IMF Reconnection Event

In this study we explore the global structure of a northward IMF reconnection event observed by the Cluster and IMAGE spacecraft on March 18, 2002. In a previous paper we analyzed magnetic field and electron and ion moments to infer the instantaneous structure and size or a reconnection site local to the null region. Using simulation studies, DMSP data, and Iridium data, we examine the same event not at Cluster spacecraft separation and magnetopause thickness length scales, but at global separator length scales. The simulations posit a separator at the position of the Cluster spacecraft and 3-D nulls near the position of Cluster. We also find that the low-altitude satellite data support sunward ionospheric convection in a region that maps along field lines to both the position of Cluster as well as the magnetopause location of the large-scale separator seen in resistive MHD simulations. Having derived a reconnection electric field from the Cluster data, we can compare its value to the DMSP polar cap potential drop to derive a length for the reconnection line perpendicular to the earth- sun line. This length can be compared to the length observed both in the simulations and in the mapping from the DMSP sunward flows. We will then compare the simulated separator structure to previous simulations and observations of global anti-parallel and component reconnection. Cluster data and simulations indicate a possible tearing mode structure, whose motion we derive from a four spacecraft wavevector analysis.