Circumhorizontal arc

A circumhorizontal arc is a type of optical phenomenon that can be seen in the sky, specifically associated with the refraction of sunlight through ice crystals in cirrus or cirrostratus clouds. It appears as a colorful band of light occurring at the same altitude as the sun but usually appears as a horizontal band or arc that is parallel to the horizon. The circumhorizontal arc is a result of the sunlight passing through ice crystals that have flat, horizontally oriented top surfaces.