johnridley | Light pillar theory verified

Back here I described a nighttime light effect that I saw on the way to work, and theorized about the cause.

Today I found verification in Astronomy, Feb '99 Pg 74, "The Sky Show" column. Quoting from the article:

It's due to the combination of streetlights and a frigid air mass full of flat-based ice crystals.
Light from unshielded sources radiates upward and hits the bottom of reflective ice crystals in the atmosphere. The light then reflects back down toward your eye. From your point of view, the light appears to come from behind the crystal as part of a column above the light source. Reflections from thousands of crystals with slightly different orientations combine to make the whole pillar--even when you can't see the source. Temperatures of at least 0*F are needed to see this effect. This is one reason why such events are rare in the more temperate coastal regions.