Description

A parhelion (plural parhelia), also commonly known as sun dog or mock sun, is an atmospheric optical phenomenon that consists of a bright spot to one or both sides of the Sun. Two parhelia often flank the Sun within a 22° halo.

The parhelion is a member of the family of halos caused by the refraction of sunlight by ice crystals in the atmosphere. The prerequisite ice crystals occur with cirrus or cirrostratus clouds. It is the occurrence and placement of these clouds that determine the parhelion appearance.

Parhelia typically appear as a pair of subtly colored patches of light, around 22° to the left and right of the Sun, and at the same altitude above the horizon as the Sun. However, they can also be extremely bright (mock suns) and one can be brighter than the other. At times, only one may occur.