- Plate crystals, Columnar crystals
- horizontal
- Reflection at the upper basal face
- quite rare (2-8 days per year)
Description
Type of crystals:
The lower light pillar is a vertical beam of light below the sun. It has about the same width and color as the sun. It is only visible while the sun is above the horizon. In addition, the ice crystals must be below the eye level of the observer, for example in ice fog, on mountains or when observing from an aircraft. Since the observer has to be above the crystal layer, the lower light pillar is rare. It often appears together with the subsun. The subsun forms on the same plates when they are less tilted.
Origin
The lower light pillar is created by the reflection of sunlight on the nearly horizontal upper faces of the ice crystals, on the base faces of plates and on the prism faces of columns. A prerequisite is that the crystals swing slightly about the horizontal position as they fall. The more they wobble, the longer the pillar becomes. In addition, a light pillar can also be caused by snowflakes. The formation of the pillar is comparable to the path of light created by the setting sun on a shimmering water surface.
Photos
Lower Light Pillar on 18.01.2013 (Photo: Hermann Koberger)
2014-03-25 - Lower Light Pillar
This lower light pillar was observed on March 25, 2014, on the Zugspitze. (Video: Stefan Rubach)
Lower Light Pillar (Photo: Claudia Hinz)