Fig. 3
From: Auroral substorms as an electrical discharge phenomenon
a The six meridian chains of magnetometers which were set up by international efforts. b An example of changes of the ionospheric current during a typical substorm (Kamide et al. 1982). c The comparison between the polar cap index (which reveals magnetic disturbances inside the polar cap), the AE index and the power ε. Note that the AE index responds to the power ε when it exceeds 1018 erg/s