Observations of Halo Scattering From Single Ice Crystals

Ice crystal haloes surrounding the sun and moon are a common sight. The most frequently observed halo occurs at 22°; a less frequent occurrence is the 46° halo. Also, rings of unusual radii have been seen and recorded. Although some are very rare phenomena, a host of other haloes, i.e., parahelia, arcs, pillars, the circumscribed halo, etc, have been observed. A comprehensive theory that encompasses all of these light-ice crystals interactions does not yet exist. Until a practical calculational method is developed, we have to rely totally on empirical evidence.