Shock Wave from a Release of Gas at 110 km Altitude

AT evening twilight on May 25, 1965, 4.5 kg of gaseous nitrogen dioxide was released at a height of 110 km from the Australian Aero-High sounding rocket. Two new observations are reported here. There was a visible glow cloud and, very surprisingly, a wave was observed expanding outwards from the glow. This wave is shown in Fig. 1, which is reproduced from a photograph taken by the Baker–Nunn camera at Woomera 13 sec after release of the nitrogen dioxide. At this time, the diameter of the wave was 11.8 km.