Back in the Neolithic Period, when WC was in high school in Fairbanks, the fire alarm went off one freezing cold afternoon. We all trooped into the -35°F temperatures to stand around, baffled why we were freezing our asses off in the absence of any trace of a need to evacuate. Eventually, we were let back inside. Over the sound of our teeth chattering, we listened to the Ass’t Principal tell us he’d sent us outside to a see a full sun halo. You can’t make this stuff up.
Here’s a really crappy photo of a 22° Sun Halo, taken through WC’s office window about 1:15 PM AST on February 6, 2015:
A Sun Halo is sun dogs on steroids, extending all the way around the sun instead of two bright spots or bright columns on either side of the sun. A Sun Halo is created by flat, hexagonal ice cystals hanging in the air. The ice crystals refract the sunlight; as in a regular prism, different frequencies of light get refracted slightly different amounts: 21.54° for red light and 22.37° for blue light.
So in the halo above, the inner border is slightly reddish and the outer border slightly bluish. Because a lot of light insider 22° is refracted, it’s slightly darker inside the circle.
And you got to see this one without having to stand outside at -35°F in your shirt sleeves.