Glory (optical phenomenon)
NASA photo
A glory is an optical phenomenon produced by light scattered back toward its source by a cloud of uniformly-sized water droplets. A glory can have multiple colored rings. The angular size is much smaller than a rainbow, about 5ÃÂð to 20ÃÂð, depending on the size of the droplets. Since it is seen in the direction opposite the sun it is most commonly observed while airborne, with the glory surrounding the airplane's shadow on clouds.
A historical name for this phenomenon is the Brocken Specter or Specter of the Brocken. The name derives from the Brocken, the tallest peak of the Harz mountain range in Germany. Because the peak is above the cloud level, and the area is frequently misty, the condition of a shadow cast onto a cloud layer is relatively favored. The appearance of giant shadows that seemed to move by themselves due to the movement of the cloud layer (this movement is another part of the definition of the Brocken Specter), and which were surrounded by optical glory halos, may have contributed to the reputation the Harz mountains hold as a refuge for witches and evil spirits. In Goethe's Faust, the Brocken is called the Blocksberg and is the site of the Witches' Sabbath on Walpurgis Night.
http://www.sundog.clara.co.uk/droplets/glory.htm