Fig. 8From: Thermospheric wind variations observed by a Fabry–Perot interferometer at Tromsø, Norway, at substorm onsetsPolar plot of wind variations for all four events. All eastward components showed increases, as indicated by the blue arrows. The northward components as indicated by the green arrows showed decreases except for the R3 event at midnight. The biggest wind variation was 48.9 m/s (eastward component of R2 event)Back to article page