Fig. 10From: Simultaneous observation of auroral substorm onset in Polar satellite global images and ground-based all-sky imagesSAMNET ground magnetic observations near the substorm onset longitude below 60 MLAT. The format is the same as that of the IMAGE magnetic observations in Fig. 9a, except that the 1-s values are shown and the average of the displayed interval was subtracted for each observatory. Pi2 and positive bay began at 2128:50 UTBack to article page