ORIGIN OF KERNS ARC

With the aid of computer-simulated halo patterns, we show that Kern's are, as seen on the latitude of the circumzenithal are and on the othe r side of the zenith, is produced by double-plate ice crystals with a vertical principal axis. Light rays that contribute to Kern's are are demonstrated by geometric ray tracing. We also discuss the condition u nder which an are that is opposite a circumhorizontal are can appear. (C) 1997 Optical Society of America.