Anticorona or Glory
January 20, 2003
The colored rings centering on the shadow of the aircraft from which this photo was taken are known as an anticorona or "glory". When cloud water droplet size is uniformly small (less than 50 microns) light grazing the edge of the droplet is diffracted into the droplet, is reflected once, and then exits via diffraction reversing its inbound direction. Glories are seen fairly commonly from aircraft. Before the days of flight, glories were a much rarer phenomena, depending on the special geometry of illuminated clouds or fog that might be found in a mountainous region. Rather than an airplane shadow, imagine the shadow of a human figure floating on the clouds, surrounded by rings of color! The Specter of the Brocken is named after the peak in the Harz Mountains of Germany where conditions conspire to produce these eerie diffraction retroreflection shadows for ground observers. Wherever it presents itself, the glory is a sight to please the observant.