From Earth Science Picture Of The Day; March 2, 2014:
Halo Display at Snowbird, Utah Photographers: David Sharp, Lisa Verzella; Summary Authors: Lisa Verzella, Jim Foster
The photo above shows a bounty of colorful halos and arcs captured at Snowbird, Utah on December 14, 2013. Sunlight shining through hexagonal plate and columnar (pencil shaped) ice crystals, found in cirrus clouds, usually give rise to these attention-getting halos. However, because of snow nucleation additives used in snow machines/snow guns at many ski resorts the ice prisms that result have nearly perfect hexagonal shapes. Downwind of the snow making machines, remarkable halo phenomena can on occasion be observed. The most prominent halos and arcs featured above include, from top to bottom, a supralateral arc, Parry arc, upper tangent arc, 22 degree halo, a blinding sundog, and a parhelic circle. Always use extreme caution when looking toward the Sun. Photo taken with an Android phone HTC One.