Photos: What are light pillars?

By Chaffin Mitchell, AccuWeather staff writer

Light pillars, or columns of light beaming to the sky, are a spectacle that awes onlookers. Conditions must be just right for these stunning lights to form.

The spectacle made news recently after appearing over Canada's night sky.

Light pillars are an optical phenomenon caused when light is refracted by ice crystals. These lights tend to take on the color of the light source.

"They appear as beams of light to the observer. It is usually caused by street lights. However, any source of light can create a light pillar given proper conditions," AccuWeather Meteorologist David Samuhel said.

For ice crystals to form, the conditions need to be extremely calm and cold, without wind. For the light pillars to show, the ice crystals need to be near the ground.

"Typically, ice crystals are small enough to remain suspended in the air and only form when temperatures are below zero [F]," Samuhel said. "In most instances, temperatures are minus 10 to 20 degrees or colder."

Samuhel said the pillars occur under high pressure without any storm present.

"There is no tie between storms and the pillars," Samuhel said. "A storm system would disrupt the pillar formation with wind and precipitation."

The source of most pillars are man-made, for example street lights and other ground light sources. They differ from auroras for many reasons, but most people have heard of auroras because they cover a much larger area.

"Auroras are observed across a much wider area, since they occur many miles up in the atmosphere. Light pillars occur close to the ground in the lowest levels of the atmosphere," Samuhel said.

As far as Samuhel knows, light pillars do not show up on radars.

"If you can predict cold and calm conditions, you can probably forecast when light pillars are able to be seen. But, the forecasting of ice crystal formation is more difficult," Samuhel said.

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Light pillars have been spotted in the United States. However, they typically occur farther north.

"I believe people have not heard nearly as much about light pillars due to the fact they are mostly observed in very cold climates where few people live," Samuhel said.

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