Ground Halo, Norway

Lars Brubæk pictured this perfect 22° ground halo on Lake Fosterlågen, near Molde, Norway.

"
We had had a long cold spell, no clouds or precipitation except a light dusting of snow on the previous night.

My wife and I were on the lake, kick sledding and skating, respectively. As we got near the lake, this sparkling ground halo became very obvious, a true eye-catcher. I took several photos, this is one. The file is made from one exposure, hand-held. Treatment in Lightroom: exposure reduced 1,55 steps, colour temp adjusted a trifle towards colder."

©Lars Brubæk, shown with permission.

Atmospheric
Optics
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Like its counterpart in the sky, the 22 degree radius ground halo is the collective glints of sunlight from innumerable hexagonal prism ice crystals. They are randomly or near randomly oriented. The hexagonal prisms might be individual crystals or components of cluster crystals.

The glints give vivid proof that the halo is not a ring. Its inner coloured edge is 22° radius but it actually extend far further from the sun.

To the unbiased eye or camera the halo is a circle. Halos, like rainbows, have the same size and shape regardless of the distance of the glinting crystals (or in the case of rainbows -raindrops). But.. ..add visual landscape cues and the halo hints at the path of the specks of light on the ground, a hyperbola, the section of the 22° half angle halo cone produced by the intersection of the ground plane.