Fig. 9From: Thermospheric wind variations observed by a Fabry–Perot interferometer at Tromsø, Norway, at substorm onsetsSchematic of wind variations on the night-side of the Northern Hemisphere expected from the diurnal-tide model at an altitude of 300 km. The eastward component shows continuous decrease from the pre-midnight to post-midnight sector and a change of direction after the midnight. The northward component shows decrease (increase) before (after) the minimum value. The times of zero crossing and minimum value for eastward and northward components are located in the post-midnight sector around 2–3 LTBack to article page