Experimenting with Minnaert's Cigar

We have studied the seldom-seen halo phenomenon that can arise in divergent light, Minnaert's Cigar, which we produced in laboratory experiments and c omputer simulation. In the laboratory experiments halos or transections wer e produced in clouds of alum crystals precipitated in a solution of ethyl a lcohol or in alum crystals deposited upon glass plates. The three-dimension al cigar form was less pronounced in our small-scale experiments than when the form was observed over several meters. In our experiments and simulatio ns transections through Minnaert's Cigar include different halo forms that may arise on window panes or windshields covered with halo-active ice cryst als or as horizontal halos on glittering frost-covered ground. (C) 2000 Opt ical Society of America OCIS codes: 010.1290, 010.2940, 010.3920.