sunhalo

A sun halo is an optical phenomenon that occurs when sunlight is refracted by ice crystals suspended in the atmosphere. These ice crystals, typically in the form of hexagonal prisms, act like tiny prisms, splitting the sunlight into its component colors, much like a raindrop creates a rainbow. The most common form of sun halo is a bright ring around the sun, often appearing at a distance of 22 degrees from the sun. This 22-degree halo is caused by light passing through the sides of hexagonal ice crystals.

Other less common sun halos can also be observed. These include sun dogs, which are bright spots of light that appear on either side of the sun, and circumzenithal arcs, which are vibrant, upside-down rainbows that can be seen high in the sky. The appearance and intensity of sun halos depend on the size, shape, and orientation of the ice crystals, as well as the angle of the sun. They are most often seen when cirrus or cirrostratus clouds are present, as these cloud types are composed of ice crystals. While visually striking, sun halos are a natural atmospheric effect and do not indicate any particular weather event, though their presence can sometimes suggest that precipitation may be on the way.