Subsun

Subsun

A subsun or "sub-sun" is a glowing spot seen within clouds when the clouds are observed from above. The subsun appears directly below the sun, as if it were caused by sunlight reflecting from a body of water. The reflection is caused by large numbers of flat ice crystals. Unless disturbed by turbulence, flat ice crystals such as snowflakes will orient themselves parallel to the Earth's surface as they fall. The region of ice crystals acts as a large mirror, creating a virtual image of the sun which appears below the horizon.

External links

* [http://www.atoptics.co.uk/halo/subhor.htm Atmospheric optics: subhorizon arcs]
* [http://epod.usra.edu/archive/epodviewer.php3?oid=121376 EPOD: striking subsun]


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