Fig. 2
From: Using ultra-low frequency waves and their characteristics to diagnose key physics of substorm onset
North–south slices (keograms) from the GILL THEMIS ASI and GILL NORSTAR MSP from 05:30:30 to 06:30:30 UT. From top to bottom, the figure shows data from the white-light GILL ASI, together with the 6300 A (red), 5577 A (green) and 4861 A (blue) emission lines from the GILL NORSTAR MSP. The orange vertical line denotes the first observation of ULF waves during this interval, at 06:04:20 UT, discussed later in the text