Light pillar is a natural phenomenon in which a vertical stream of light extends above or below a light source. When the source of light is the sun, the phenomenon is called a sun pillar. The sun pillar phenomenon is usually seen when the sun is low on the horizon or just below it. Light pillars may also be formed from the light of the moon or from artificial sources like streetlights.
The light pillar phenomenon takes place when ice crystals with roughly horizontal planar surfaces are present in the atmosphere. These ice crystals reflect the light from the source resulting in the formation of a light pillar. Because the light rays forming pillars are reflected, they take on the color of the incident light. Hence in case of sun pillar phenomenon, if the sun is higher in the sky, the sun pillar will appear white or bright yellow and if it is near the horizon, the pillar will appear red or orange.
The light pillar phenomenon is frequently observed near Niagara Falls in winters months as the city’s upward facing spotlights interact with the ice crystals in the mist from the Niagara Falls to create multiple light pillars.