Field-aligned current density determination with Swarm for finite and non-planar current sheets

Abstract:

To calculate field-aligned current densities from a single or two-spacecraft technique, one usually assumes an infinite and planar current sheet. The method consists then in inferring the current density from one single component of the curl of magnetic field vector. We present an analytic refinement which takes into account the effect of the possible curvature of the current sheet in the determination of the field-aligned current density. We first show synthetic cases with current sheets whose curvature radii are known. We show that the results are significantly affected below some threshold. We then discuss the possibility of estimating the radius of curvature with real data from two-point measurements like the Swarm fleet can offer. We eventually apply our method to the calculation of the FAC density.