Circum-horizontal arc

Cincun-horizontal arc, also known as fire rainbow, is an optical phenomenon very similar to the circunzenital arc, and is caused by the refraction of light through ice crystals in Cirrus clouds. The difference is that it occurs only when the sun is high in the sky, at least 58 degrees above the horizon, and can only occur in the presence of Cirrus clouds. The phenomenon is quite rare, as ice crystals must be aligned horizontally to refract the high sun. The arc is formed as the rays of light enter the hexagonal flat crystals. It is the 90 ° tilt that produces the rainbow colors, well separated, and if the alignment of the crystals is very correct, all the Cirrus clouds shine like a flaming rainbow.