A spectral
halo with an
angular radius of about 46º occasionally seen in a
cirrostratus around the
sun or
moon. Like the
22º halo, it is caused by refraction through randomly-oriented
ice crystals and is sometimes accompanied by
sun dogs - brighter, more colourful patches at or just outside its edge.
The 46º halo is much rarer and fainter than the 22º version: It is only seen when the ice crystals are just right. Either kind of halo is a sign of low pressure coming in, and often means there is rain and other wintry weather on its way.
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