As another arctic air-mass invades the Red River and Lakes Region, we're being treated to a relatively rare atmospheric event. Double Solar Halos, also known as "Sun Dogs", are the result of ice crystals suspended in the atmosphere. While solar halos are not uncommon, double halos are less frequent. Typically the first halo is located about 22 degrees (tangental) from the sun or moon; the more rare, second halo, is located at about a 46 degree arc from the Sun or Moon. Halos are optical phenomenon which are produced by certain types of suspended ice crystals, resulting in multi-colored arcs or spots in the sky. Halos are most common near the Sun or Moon, with others elsewhere in the sky. Some are even visible in the side opposite of the light source. The exact process is known as refraction, where the light is bent (refracted) and split into its myriad of base colors. Rainbows are a form of halos.
Below are a couple of pictures taken at the Grand Forks NWS Office around 1130 am Thursday morning. At the time the pictures were taken, there was a great deal of suspended ice-crystals in the atmosphere. This is a commom occurrence on the leading edge of very cold arctic air-masses. As winds subside and the region is more fully involved in the arctic air, the Sun Dogs will fade. Within the Valley and Lakes region, the appearance of Sun Dogs is often seen as a portend of a very cold night.
Solar Halo picture taken from NWS in Grand Forks (looking south) The sun is just off the bottom of the photo. (Click on the image for a larger version)