From: Steve (Primus) (Avatar) 30/10/2001 5:49:53 Subject: re: STEVE'S WEATHER FAQ post id: 476420 In Brisbane, at around 3:40 pm, there was a partial rainbow about 15 degrees to the north of the sun, with the sun at its centre. Can anyone explain this phenomenon? There was a lot of cirrostratus and cirrus cloud around today and various halo phenomena were seen. I was in Casino in northern NSW this morning and there were two beautiful sundogs or parhelia - like small rainbows either side of the sun. I cannot speak for Brisbane, as I was not there but it would have been a type of halo that you saw. That is a parhelion or sun dog, There were two absolute beauties at Casino yesterday morning. Today we had one of the most spectacular coronae and associated irisation I have ever seen.It formed in bands of cirrocumulus cloud over the area. With the band of high cloud currently over northeast NSW and southeast Queensland, people in the area should keep an eye on the sky for some great phemomena. Min Mins lights Does anybody know the scientific reason behind these things? There are two major ideas about the cause of the min-min lights which, traditionally, are seen near Boulia in southwest Queensland but have been seen in many parts of Australia. The older theory is the natural gas one. Bubbles of methane spontaneously ignite producing the lights. The will-o'-the-wisp in the UK is associated with swamp gas and the min-min lights have been thought to be similar. Unfortunately will-o'-the-wisps occur in wet swampy areas while the min-min lights occur in the dry interior of Australia. The second, and much more recent, theory is the one I prefer. Australia's climate is dominated, as I have mentioned many times before, by the sub-tropical ridge. This is a belt of high pressure. In high pressure systems the air is descending and warming as it does so. This creates a temperature inversion - a layer of air where temperatures increase with altitude rather than decrease. Subsidence inversions are common and long lasting. Radiation inversions, caused by the cooling of the earth overnight, are shallower and short lived. The density of the air above and below the inversion is quite different and the density change can reflect light - much as the surface of a swimming pool viewed from below looks like a mirror. The movement of the air near the inversion distorts the reflections so that the original source of the light being reflected is unidentifiable. It could also be 100 or more kilometres away from where you see the light. Reflections off inversion layers are responsible for a lot of UFO sightings and "strange lights in the sky" and, very possibly, the min-min lights. Have you been underwater in a swimming pool and looked at the surface? The surface looks like a mirror. The different density of the water and air produces a reflective layer. Air at different densities does the same thing. Usually the angle between the light source and the observer needs to be very large so that the original light is a long way away. All you see is the reflection, somewhat distorted, and not the original light.