From Glossary of Meteorology
Small, faintly colored rings of light surrounding the antisolar point, seen when looking down at a water cloud.
Having a radius of only a few degrees, the glory often surrounds an airplane's shadow cast on a cloud or a mountain climber's shadow cast on fog in a valley. (The shadow of the observer plays no role in the phenomenon other than as easy way of quickly finding the antisolar point.)The glory is not as easily described by simple theory as is the corona. Nevertheless, some similarities hold: the angular size of a particular ring is approximately inversely proportional to drop size. The result is that glories are formed by droplets with radii smaller than about 25 μm (the rings from larger droplets are washed out by the angular width of the sun). Similarly, a broad droplet distribution will destroy the glory.