Diamond Dust Halos imaged by Bogdan Kossewski at Zakopane, Poland. Image ©Bogdan Kossewski, shown with permission.
Here we can really believe that halos are made by the individual glints of millions of ice crystals. Both of these halos are from rays passing between crystal faces at right angles to one another. They are called '"46° arcs" because that is the angle of minimum deviation or refraction under those conditions. The upwards pointing halo is an "upper symmetric 46° plate arc" more popularly known as a circumzenithal arc and generated in this case by plate crystals. The downwards curving halo is made by column crystals and is a "46° column arc" or supralateral arc.
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