Abstract

Halo phenomena comprise a surprisingly large variety of arcs and spots in the sky. Most of the observed phenomena are explained in the framework of geometrical optics by a single scattering of the sunrays at hexagonal ice crystals/1/. The repeated scattering of sunrays by two or three crystals is proposed to explain a few rarely observed phenomena like the cross in the sun region and the double structure of the subsun/2/. The trouble is that in most of these cases an alternative explanation can be given; i.e. the cross may be produced by diffraction scattering/3/.

© 1986 Optical Society of America