Wiktionary
light pillar
n. A visual phenomenon created by the reflection of light from ice crystals with near-horizontal parallel planar surfaces.
Wikipedia
Light pillar
A light pillar is an atmospheric optical phenomenon in the form of a vertical band of light which appears to extend above and/or below a light source. The effect is created by the reflection of light from numerous tiny ice crystals suspended in the atmosphere or clouds. The light can come from the Sun (usually when it is near or even below the horizon) in which case the phenomenon is called a sun pillar or solar pillar. It can also come from the Moon or from terrestrial sources such as streetlights.
Usage examples of "light pillar".
It is the largest room in the world, and is unbroken save by the light pillars which support the floors above.