My Twitter feed exploded on June 25 with reports of colorful, crazy-looking clouds, sundogs, Sun halos and more. The above image from Nathanial Burton-Bradford is just an example of the type of atmospheric effect called a circumhorizontal arc. These are sometimes referred to as “fire rainbows” but of course are not rainbows, and fire plays no role.
This is an optical phenomenon from sunlight hitting ice crystals in high cirrus clouds. It is actually a rather rare occurrence, but it happens most often during the daytime in summer when the Sun is high in the sky. This creates a rainbow-type effect directly in the ice crystal-filled clouds.
Fresh off seeing a solar eclipse on Sunday, people across the southern parts of Africa witnessed another solar spectacle today, a sun halo. “It was so beautiful, everyone was taking pictures and sharing them on Facebook,” said Daniël Engelbrecht from Klerksdorp, South Africa, sending in his picture to Universe Today via email.
These halos are quite the sight to see, but unlike an eclipse, they can’t be predicted. Conditions in the atmosphere have to be just right, with moisture or ice crystals creating a “rainbow” effect around the Sun. Sometimes the halos surround the Sun completely, other times, they appear as arcs around the Sun creating what is known as sundogs. Basically, sunlight is reflecting off moisture in the atmosphere.
Ice crystals in Earth’s atmosphere can also cause rings around the Moon, and moondogs(as well as sundogs) and even Venus pillars. News reports indicate sun halos were seen just a few days ago in Africa as well, on Nov. 1, 2013.
A few other people sent in images from their phones, too of today’s sun halo: