Sundogs & Subparhelia Images by Michael Plouffe (mpaviation) at 39,000ft over Alberta, Canada.

All images ©Mike Plouffe, shown with permission
Almost the same rays produce sundogs and subparhelia. Sunlight enters a crystal side face and leaves through another inclined 60° - a 60° prism.

But, unlike the sundog ray paths usually shown, the rays are reflected internally several times from the upper and lower crystal faces.

An even number of reflections gives a sundog, an odd number a subparhelion below it.

Mike's display was likely produced by wobbly and relatively thin hexagonal plate crystals. The HaloSim ray tracing used plates with a Gaussian distribution of wobbles of standard deviation 12°. Such crystals are also the stuff of sun pillars and bright upper and lower pillars were present.

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Always check the opposite part of the sky.

Antisolar (anticrepuscular) rays and shadows converge towards the antisolar point.

The diagonal stripes are scratches - it seems that even pilot's windows have them.