Montana Halos ~ Above and below horizon ice halos captured by Marc Roston at Whitefish, Montana.

A 22 halo circles the sun. The sun is crossed by a parhelic circle and rarer helic arcs. A lower tangent arc blazes at the base of the 22 halo. From it stretches an infrequently glimpsed lower Wegener arc. Colour streams downwards from a sundog to meet a fainter subparhelion.

All images ©Marc Roston, shown with permission
A Parry arc glints in diamond dust above an upper tangent arc

A HaloSim ray tracing of the display. It used randomly oriented hexagonal columns to generate the 22 degree halo.

Singly oriented columns made the intense upper and lower tangent arcs. In reality the UTA was less bright, probably because there were fewer diamond dust crystals along the upwards line of sight.. The same horizontal columns gave the supralateral, infralateral and Wegener arcs.

A few Parry oriented columns produced the Upper suncave Parry and the helic arcs radiating from the sun.

Wobbly plate crystals completed the display to make the parhelion, subparhelion and subsun. The 'join' between the sundog and subdog comes out faint in ray tracings.

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Twice as far from the sun as the 22 halo are colourful supralateral and infralateral arcs.