This leads me to believe that it is indeed a
circumzenithal arc captured in the image, an optical effect formed as light refracts off ice particles in thin cloud at high levels.
We call them pseudo-circumzenithal arcs, or PCZAs, because the ray paths are similar to those that form the beautiful, rainbowlike
circumzenithal arcs on Earth.
Today, it's true, we seldom hear the
circumzenithal arc described as being "of Bravais," or a well-developed fogbow referred to as "Ulloa's ring." But some of these sky effects are too complex or rare for the names of their classic observers to be deleted.
The spectrally colored arc with its back to this may have been the faint "upper tangential arc" of the "circumscribed halo." If it was not nearly in contact with the first arc, it could have been the more colorful "
circumzenithal arc," which really does seem like an out-of-place rainbow in a rainless sky.
Using only a point-and-shoot camera he was able to capture a richly colored segment of the
circumzenithal arc that appeared about 65 [degrees] above the Sun (see page 103).
Like its more common cousin the
circumzenithal arc, this display is formed by refraction of sunlight in ice crystals of cirrus and high haze, which can be present year around.
Common rainbows are caused by light shining through raindrops but
circumzenithal arcs appear when light is refracted through ice crystals higher up in the atmosphere.
Unlike rainbows, where sunlight refracts through raindrops,
circumzenithal arcs occur when sunlight refracts through ice crystals in cirrus clouds.
When was the last time you glanced up on a sunny day to check for rings around the Sun, or any colorful
circumzenithal arcs or iridescent clouds?