In Belgium, sky watchers were stunned when they witnessed a heavenly apparition in broad daylight. "It was one of the brightest and most complex displays of sun haloes I have seen in 25 years of observing," reports Philippe Mollet, who took this picture:
Sun haloes are caused by ice crystals in high clouds. "This wonderfully bright display proves that you do not need to be in polar regions to see them," notes atmospheric optics expert Les Cowley. "Temperatures in 3 to 6 mile high cirrus are more than cold enough to make the needed hexagonal prism shaped ice crystals. There are two sets of halos, those nearest the sun are made by rays that pass between crystal faces inclined at 60 degrees. The outer halos with widely separated colors are from faces inclined at 90 degrees. See the labeled image for halo names. The huge colourful halo is a supralateral arc. This halo is often very hard to distinguish from the much less common 46 degree circular halo but there are several clues to look for to tell them apart."
From Philippe Mollet, and from Hendrik Mertens of Londerzeel, Belgium