Today’s post I suspect will be in the “You learn something new every day” category for most readers. Here’s an explanation of this phenomenon pieced together from Pillars at Atmospheric Optics and Wikipedia’s Light Pillar entry (more photos at both links and the one below).
A sun pillar (or light pillar or solar pillar) is a visual phenomenon created by the reflection of light from ice crystals with nearly horizontal parallel planar surfaces. The hexagonal plate-like ice crystals fall with a horizontal orientation, gently rocking from side to side as they fall.
The light source can be the Sun (usually low to the horizon), moon or manmade sources like streetlights. Niagara Falls is a common place to see them as the mist from the Niagara Falls causes the phenomenon to appear frequently during the winter months, when ice crystals interact with upward facing spotlights to create prominent light pillars.