Greenland Halos - Photographed high on the Ice Cap at Summit Station by Ed Stockard (images) on 25th August '11.  ©Ed Stockard, shown with permission.

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Good halos require crystal habit - habit - habit and orientation - orientation - orientation.    Location does not matter, they can be found anywhere in the world and possibly elsewhere although it must be admitted that diamond dust, seen here as individual crystals glinting their rays, confers an advantage to polar regions.

Random or pseudo randomly oriented crystals or clusters produced the 22 and 46 degree radius circles around the sun.

'Singly oriented columns gave the common upper tangent arc, the less common infralateral and supralateral arcs and the rare Wegener and subhelic arcs.

Plate oriented crystals contributed the sundogs, the 120 degree parhelia and the circumzenithal arc.

The parhelic circle girding the sky came from all orientations except the randomly tilted ones.
HaloSim simulation