The formation mechannism of elliptical halos and Bottlinger's rings has long remained uncertain. The current model for elliptical halos requires multiple scattering from two different populations of ice crystals in a complex mode of motion. New evidence indicates that elliptical halos, and possibly Bottlinger's rings, are due to refraction through ice crystals shaped like obtuse pyramids. This unusual ice crystal may not have been documented previously.
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