MY DAD took this picture just last week. (He may have been using a polarizer, but it was plain to the naked eye. Stopped traffic for several minutes as everyone just stood staring at the sky!) Ice crystals in the cloud are reflecting the sun's rays. I'm sure there's a name for this beautiful event, but of course my meteorology book is buried somewhere in the 'forbidden zone' (the garage). Whatever you call it, it's amazing!