The Sun pillar is a bright column that extends from the solar disk downward or upward and can also occur with the Sun close to the horizon. The cause is the reflection of sunlight by horizontal ice crystals.
It can be clearly visible in cirriform formations near the horizon in every month of the year and in icy fogs during the winter months. In Italy it can easily form on the large humid plains of the North at dawn or at sunset. The clouds that generate it are generally made of thin, broad ice crystals like tiny mirrors that reflect the light. Often before sunrise the sunlight begins to illuminate more and more these tiny ices with the solar disk still below the horizon. Dawn colors turn deep red. The ice crystals move slowly in the air like leaves falling in autumn, staying parallel to one another. However only the few that are in a horizontal position reflect sunlight toward the observer and thus light up the sky more intensely above the Sun, making the whole sky redden.
For Sami culture a solar column was a divine sign. When it appeared in the sky it was forbidden to leave one’s land at least until the solar disk would reappear free of the photometeoric formation. Also in its presence it was forbidden to whistle and shout, since it was attributed a sacred cause not interpreted scientifically.
The sun pillar is only a special type of light pillar. The light pillar is a completely natural luminous effect: colored columns of light that can be admired in the skies of very cold areas of the Planet. The phenomenon is produced by the interaction between light sources, such as car headlights, and suspended ice crystals. When there are heavy snowfalls with wide, flat, star-shaped flakes, light pillars can be seen along roads on moving cars even before seeing the car headlights.
Photo by Gianni Giannerini
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