Pyramidal Ice Halos

March 08, 2003


Referred by: Michael Ellestad
Summary authors & editors: Jim Foster; Michael Ellestad

The above photo shows a pyramidal halo complex taken over southern Ohio (Adams County) on May 25, 2002. Close inspection of this photo reveals that halos of 9 degrees, 18 degrees, 22 degrees, and 24 degrees are visible around the Sun. The 9 and 18 degree halos exhibit parhelia or sundogs. While hexagonal ice crystals are responsible for the formation of the 22 degree halo, pyramidal ice crystals are required to form more exotic halos, including 9 degree and 18 degree halos. Pyramidal crystals have one or both end faces of ordinary ice crystals replaced by six-sided pyramids.

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