Pillar Above Cluj-Napoca, Romania

August 08, 2005


Provided and copyright by: Cristina Tinta, Romanian Society for Meteors and Astronomy
Summary authors & editors: Cristina Tinta

The above photo showing a prominent, upper Sun pillar was taken on April 17, 2005 from the balcony of my home in Cluj-Napoca, Romania. Hexagonal plate and column-shaped ice crystals are responsible for pillar phenomenon. Plate crystals generally produce pillars only when the Sun is within 6 degrees of the horizon, or below it; column crystals can generate a pillar when the Sun is as high as 20 degrees above the horizon. Crystals tend to orient themselves horizontally as they fall or float through the air. The width of a pillar is a function of the extent to which the crystals wobble about their vertical axis and is unrelated to crystal size.

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