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Desert Sun Halo

On April 19th, 2001, the sun over the Mojave Desert was encircled with a 22 degree halo. The following shots show what could be seen. Click on a thumbnail for an enlarged picture.
Each of these pictures includes the top of a twenty-five foot tall juniper.

The halo completely surrounds the sun, even though these pictures do not show the entire phenomenon.

Halos can be bright white rings, or colored.
This and the next pictures were taken with a slightly different shutter setting, hence the darker appearance.

The halo comes from light refraction (bending), through ice crystals in the atmosphere, between the sun and the earth (observer). Usually the ice crystals are in thin, high-level clouds, either cirrus or cirrostratus.

Ice crystals bend the light as it enters and leaves, for a total of 22 degrees refraction.
A jet trail, at about 30,000 feet elevation, streaks across the lower half of this photo. Jet trails are formed from ice crystals.

Ice crystals bend the sun's light twice, once on entering the crystal and again on exiting the crystal. The amount of bend (refraction) depends on the diameter of the ice crystal. For 22 degrees refraction, ice crystals are less than 20.5 micrometers.
Joshua tree limbs underline the solar/atmospheric display.

Not appearing here, but occasionally, a second halo can be seen at 46 degrees outside the 22 degree halo.
Same as above, but with a filter added.
What you aren't seeing is spectacular!

Pictures on this page may be taken and used freely, for personal or commercial use.

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