#DIAMOND #DUST #SKI #HALO: Ski resorts are great places to see sun halos--rings of light that surround the sun when ice crystals fill the air. Spaceweather.com reader Christian Schartner was skiing at Reiteralm ski resort in #Austria this morning when he witnessed this specimen:

" #Winter has finally returned to Austria," says Schartner. "Today, I skied at -10°C. Several nearby snow cannons created sparkling #crystals, creating the perfect conditions for 'ski halos.'"

Snow cannons were key to this display. Ordinary sun halos are caused by ice crystals forming naturally in high cirrus clouds. Snow making machines create a spcial type of crystal called "diamond dust." These man-made crystals tend to be more optically perfect than natural crystals in clouds, producing extra-bright, extra-sharp halos.

A close look at Schartner's picture shows specks of light in the air. Those are the glittering crystals of diamond dust which make ski halos so beautiful.
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