Fig. 5From: Thermospheric wind variations observed by a Fabry–Perot interferometer at Tromsø, Norway, at substorm onsetsAU and AL indices for all event times, using the same format in Figs. 3 and 4. Panels a–d indicate the results for events R1–R4, respectively. Global-scale substorm onsets after the local substorm onsets can be identified in b and d, while there is no obvious evidence of substorm onsets at other timesBack to article page