Subsun
Glowing spot that can be seen within clouds or haze when observed from above
A subsun (also spelled sub-sun) is an optical phenomenon that appears as a glowing spot visible within clouds or mist when observed from above. The subsun appears directly below the actual Sun, and is caused by sunlight reflecting off numerous tiny ice crystals suspended in the atmosphere. As such, the effect belongs to the family of halos. It is also known as a "sun candle".
01Formation
The subsun phenomenon appears when a region of hexagonal ice crystals act as a large mirror, creating a virtual image of the Sun below the horizon. As they fall through the air, the ice forms plate crystals which orient horizontally, i.e., with their hexagonal surfaces parallel to the Earth's surface. When they are disturbed by turbulence, the plates "wobble", causing their surfaces to deviate some degrees from the ideal horizontal orientation, and causing the reflection (i.e., the subsun) to become elongated vertically.
02Deformations
When the subsun is stretched far enough vertically, it can become a vertical column known as a lower sun pillar. A sun pillar is a form of light pillar.
Sources and credits
This article is adapted from the Wikipedia article “Subsun”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- IMG 6880 subsun.JPG by Brocken Inaglory, CC BY-SA 3.0
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