Multi-point Analysis of Current Structures and Applications

Abstract:

The Curlometer was defined as a technique for analyzing currents from multi-spacecraft data. We review its use, primarily with the four spacecraft Cluster data, its recent developments, related techniques and new applications derived from the calculation of curl B and magnetic gradients to compare estimates of the current distributions. Specifically, we explore the capability of Swarm-Cluster coordination for probing the behavior of the field aligned currents (FAC) adjacent to the ring current (RC) at medium and low orbits and show statistical analysis of the local time variation of R1/R2 FACs. The RC and connecting R2 FACs influence the geomagnetic field at low Earth orbit (LEO) and are sampled in situ by the four Cluster spacecraft. Coordination of the configuration of three Swarm spacecraft configurations with the constellation of the four Cluster spacecraft is possible; providing a set of distributed, multi-point measurements covering this region. Joint signatures of R1 and R2 FACs can be confirmed. Multi-spacecraft analysis can also access perpendicular currents associated with the FAC signatures at the Swam locations. For context, we identify the associated auroral boundaries through application of a method to determine the FAC intensity gradients in order to interpret and resolve the R1 and R2 FACs. We also show preliminary results of an extended survey of the ring current crossings for different years, including events during non-storm and storm times, estimating the local current density, field curvature and total current; analysing the spatial extent of the ring current region.