Figure 1. Ground observations of aurora and electric currents.
(a) Snapshot from three ASIs at Snap Lake (SNAP), Rankin Inlet (RANK), and Sanikiluaq (SNKQ) at 6:12:30 UT. Tiny yellow lines show local velocity of auroral substructures. (b) Current system structure on the ground: snapshot of EICs (arrows) and the SECS scaling factors (color: upward in reddish, and downward in bluish) at 6:12:30 UT, calculated using ground-based magnetometer array data. The footprints of the five THEMIS probes as predicted by the AM03 model are denoted by overplotted crosses (red for P1, green for P2, blue for P3, cyan for P4, and magenta for P5; see also zoom-in).