Corona (optical phenomenon)

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In meteorology, a corona (plural coronae) is an optical phenomenon and photometeor produced by the diffraction of sunlight or moonlight, or any bright light source by individual particles larger than the wavelength of light, most commonly seen in small water droplets, tiny ice crystals of a cloud, or condensation on a foggy glass surface. In its full form, a corona consists of several concentric, pastel-colored rings around the light source and a central bright area called an aureole. The aureole is often (especially in case of the Moon) the only visible part of the corona and has the appearance of a bluish-white disk which fades to reddish-brown towards the edge. The angular diameter of a corona depends on the sizes of the particles involved relative to the wavelength of light. Smaller particles generally produce larger coronae, while larger particles produce smaller coronae with more closely spaced rings. For the same reason, the corona is the most pronounced when the size of the droplets...

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