circumhorizontal arcs photographed by (click pic) david england, andy cripe, del zane, todd sackmann and brandonrios. this atmospheric phenomenon, otherwise known as a fire rainbow, is created when light from a sun that is at least 58 degrees above the horizon passes through the hexagonal ice crystals that form cirrus clouds which, because of quick cloud formation, have become horizontally aligned. (see also: previous cloud posts). They are one of the rarest natural phenomenons.
These are also known as sun dogs (proper name Parhelion) and I saw one once, from the ground.