Halo observations provide evidence of airborne cubic ice in the Earth's atmosphere

An ice crystal halo display that contains several previously unknown halo phenomena was observed in Northern Chile. Analysis of computer simulations of the halos demonstrates that most of the new halo arcs in the display can be explained by the presence of airborne and preferentially oriented crystals of cubic ice. These observations therefore provide evidence of the existence of the cubic phase of ice in the Earth's atmosphere. (C) 2000 Optical Society of America OCIS codes: 010.1290, 010.2940, 290.5850.