Airglow made visible by the passage of acoustic gravity waves in the upper atmosphere

This composite of 2 30 second images shows 3 quite bright bands of light in the SE sky, most likely due to the passage of acoustic gravity waves through the upper atmosphere in the 80-100km region. The bands were quite noticeable to the naked eye, although there was not any obvious colouration, the features appearing greyish. Crux appears near the centre of the image, and is a useful indicator of scale.
The lower right and to a lesser extent the whole lower part of the image is red due to weak auroral emissions in the red part of the spectrum. Aurorae seen at this latitude are generally red and at the time of the photographs, were subvisual. The green colour of the wave features is most likely due to OI airglow emission at 557.7nm.
The phenomenon of acoustic gravity waves is not in any way related to Gravitational Waves from massive objects in deep space such as Neutron Stars or Black Holes. Rather they can be thought of as oscillations of temperature and wind, with little or no change in pressure. Gravity waves can be triggered by auroral disturbances in the ionosphere, large thunderstorm towers punching up into the troposphere, and also by cyclones and kinks in jet streams. The source for the events photographed here is not determined.

E B Armstong in The Journal of Atmospheric and Terrestrial Physics, Vol 44, No4, pp325-336, 1982 presents a study of a similar display observed from Culgoora Solar Observatory in 1980.
Richard Scorer and Arjen Verkaik discuss gravity waves in Spacious Skies - The Ultimate Cloud Book
ISBN 0-85091-376-4

The above photographs were taken using Kodak Ektar 1000 hypersensitsed in 5% H2 in N2 (forming gas) in a normal 35mm camera fitted with a 55mm lens @ f/1.2. Film buckle has caused some focus softness in the left hand sides of the individual frames. Spherical aberration causes bloated star images, however this lens is excellent for recording larger scale detail such as auroral rays, and in this case, faint bands of airglow across the sky. The above photographs were obtained on 1989
December 22. Similar displays were observed on 1989 Dec 26 and 28, and 1990 Jan 23 which was notable for a particularly intense display with apparent brightness similar to the LMC ( B&W photo below).

When passing overhead the bands moved by up to 20 degrees towards the South over a 10 minute interval which indicates that the source of the gravity waves was apparently not auroral. My notes from 1989 Dec 22 (Observing from 151E, 31S, alt 450m) say that the bands of light of East-West orientation were first noticed at 11UT, and that there was a general glow in the West SW and South (probably auroral). When the fisheye lens photos below were taken, the bands of light had become fainter (just after 12UT) The bands overhead were no longer visible at 13UT, the bands then only appearing in the North and South. (above photos taken just after 13UT when the bands in the south were quite bright) (Note, "quite bright" is a relative term, the display would not have been visible in areas suffering light pollution, the intensity generally being similar to the fainter portions of the zodiacal light pyramid). On some occasions there were a dozen or more bands across the whole of the sky, the fisheye views below giving some indication of the appearance, although f/2.8 is a bit too slow a lens for recording this type of display.

More views of Acoustic Gravity Waves in the upper atmosphere

Click on the image for an enlarged view with details of the photograph