Fig. 7From: Thermospheric wind variations observed by a Fabry–Perot interferometer at Tromsø, Norway, at substorm onsetsNorthward components plotted over north–south cross sections of auroral images, using the similar format in Fig. 6. Panels a–d indicate the measurements for events R1–R4, respectively. The horizontal yellow lines in each panel show the north and south edges of the FPI scan with an elevation angle of 45°Back to article page