Atmospheric Phenomenon a solar halo

I was recently treated to a sight unlike I had ever seen before. A rare atmospheric phenomenon called a solar halo.

My first inlination that something was going on was when I stepped outside to find a huge black disc just hanging in the air above the house. Anyone who has seen the film Independence Day and remembers the mother ship hanging silently over the White House should be able to picture the sight that greeted me.

And large it certainly was. The more accurate name for this type of solar halo is a 22 degree halo, after the portion of the sky it covers.

The halo takes the form of a circular ring of bright light some distance from the sun. Then between this ring and the sun is a dark disc, almost as dark as the night sky. Inside everything at the very center is the brightly glowing sky.

The halo was made even more distinct by the rest of the sky remaining a brilliant cloudless blue. And in addition although the dark disc covered a large portion of the sky it cast no shadow.

It would be fitting to attatch some magical significance to the halo, but the truth although rare and unusual all can be explained by science.

High up in the atmosphere the suns light is refracted off of ice crystals. If these are just the right type, in just the right place and if the light from the sun strikes them at just the right angle a halo can be formed.

This light is refracted away from the sun to a point 22 degrees from the sun, beyond which the effect can not reach. There this sunlight forms a ring. Within the ring darkness is created by the light being driven from the sun to the ring of the halo.

I do not know over how wide an area the solar halo was visable, but once created it was very stable, hanging silently in the air for a couple of hours before slowly starting to fad and disperse.

Once the phenomenon passed the sky returned to how it had been before, bright blue with a shining sun and no hints that it had ever looked otherwise.

I have since read that it is sometimes believed that the appearence of a halo is a sign that rain will shortly be following. In this case at least that was not the what happened as the weather continued afterwards as it had been before. Hot and sunny.