Influences of the interplanetary magnetic field clock angle and cone angle on the field‐aligned currents in the magnetotail

Abstract

The influences of the interplanetary magnetic field (IMF) cone angle θ and clock angle ϕ on the field‐aligned currents (FACs) at the plasma sheet boundary layers (PSBLs) have been investigated using Cluster Data. The FAC occurrence increases monotonically with IMF cone angle and has two peaks at −90° and +110° clock angle, respectively. The peak at +110° is distinctly larger than that at −90°. Overall, there are more FACs between 0° < ϕ < 180°, indicating that FACs occurrence is closely associated with duskward IMF. More FACs occur when 90° < |ϕ| < 180°, implying that FAC is closely associated with southward IMF. The large FAC densities occur when 60° < |ϕ| < 120°. The density also has two peaks and the peak at +90° clock angle (duskward IMF) is larger than that at −90° (dawnward IMF). These results indicate that the IMF influence on the FACs is from all IMF components and not only from a single component.