Fig. 1

Current systems for \(B_z < -2\) nT conditions. Vertical (left) and horizontal equivalent (right) current systems estimated based on data when IMF \(B_z<-2\) nT. The figures show the regions poleward of \(50^\circ\) (top) and \(-50^\circ\) (bottom) modified apex (left) and QD (right) latitude. Noon MLT is at the top, dusk to the left and dawn to the right, which means that the view is from above the Northern hemisphere, and through the Earth for the Southern hemisphere patterns. The equivalent currents flow in the \({{{k}}}\times \nabla \Psi\) direction. \(\Psi\) is displayed at 30 kA contour spacing, and increases from dashed to solid contours. The total current flowing between the local extrema of \(\Psi\) is shown at the bottom right. This format is retained throughout the paper