Light pillars are beams of light formed by an optical phenomenon created by the reflection of light from flat hexagonal ice crystals horizontally suspended in the atmosphere.
Different shape and colour depend on the source of light, which can be natural (sun, moon) or artificial (streetlights), on the position of the crystals: the higher they are, the taller the pillars are, and on the number and dimensions of the crystals: the larger and more numerous they are, the more pronounced is the effect.
Due to the low temperature required, this effect is typical of arctic regions.