Fig. 2
From: Relation of the auroral substorm to the substorm current wedge
Characteristic changes in different variables reveal substorm development. Solar wind coupling function (a), traces of auroral luminosity (b), Pi 2 pulsation power (c), SuperMag AL index (d), and the Midlatitude positive bay (MPB) index (e) are presented in successive panels for an event on March 3, 2008. Vertical dotted lines in each panel show onset times. Spikes in luminosity indicate intensification of the aurora. Peaks in Pi 2 power show waves communicating between the tail and ionosphere. Sudden drops in the SML index show enhancements of westward current beneath the aurora. A peak in the MPB index is produced by the growth and decay of the substorm current wedge