Arctic sky show: Subzero temperatures trigger sun dogs around Minnesota

The arctic atmosphere played optical cold weather tricks above Minnesota Friday morning.

Several observers sighted and photographed sun dogs in the frigid morning air mass.

Ice and light

Sun dogs are optical phenomena caused by refraction through ice crystals in the atmosphere. They often occur at 22-degree angles from the sun and are also called 22-degree halos. Sun pillars occur directly above the rising sun.

Here’s a good description of cold weather optical phenomena from the La Crosse, Wis., NWS office.

Sundogs

Sundogs are colored spots of light that develop due to the refraction of light through ice crystals. They are located approximately 22 degrees either left, right, or both, from the sun, depending on where the ice crystals are present. The colors usually go from red closest to the sun, out to blue on the outside of the sundog. Sundogs are also known as mock suns or parhelia, which means "with the sun.”

Sun pillars

Sun pillars appear as a shaft of light extending vertically above the sun, most often at sunrise or sundown. They develop as a result of ice crystals slowly falling through the air, reflecting the sun’s rays off of them. Look for sun pillars when the sun is low on the horizon, and cirrus clouds are present.

Halos

A halo is a ring or light that forms around the sun or moon as the sun or moon light refracts off ice crystals present in a thin veil of cirrus clouds. The halo is usually seen as a bright, white ring although sometimes it can have color.

Sun dogs and other arctic optical phenomena are one of the benefits of our frigid winters in Minnesota and the Upper Midwest.