APOD: Light Pillars over Alaska (2016 Feb 08)

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APOD Robot
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APOD: Light Pillars over Alaska (2016 Feb 08)

Post by APOD Robot » Mon Feb 08, 2016 5:14 am

Image Light Pillars over Alaska

Explanation: What's happening behind those houses? Pictured here are not auroras but nearby light pillars, a nearby phenomenon that can appear as a distant one. In most places on Earth, a lucky viewer can see a Sun-pillar, a column of light appearing to extend up from the Sun caused by flat fluttering ice-crystals reflecting sunlight from the upper atmosphere. Usually these ice crystals evaporate before reaching the ground. During freezing temperatures, however, flat fluttering ice crystals may form near the ground in a form of light snow, sometimes known as a crystal fog. These ice crystals may then reflect ground lights in columns not unlike a Sun-pillar. The featured image was taken in Fort Wainwright near Fairbanks in central Alaska.

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rstevenson
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Re: APOD: Light Pillars over Alaska (2016 Feb 08)

Post by rstevenson » Mon Feb 08, 2016 1:26 pm

A question for the experienced... Can you be surrounded by these sorts of light pillars? Or are they always in the distance, as rainbows are.

Rob

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Re: APOD: Light Pillars over Alaska (2016 Feb 08)

Post by NGC3314 » Mon Feb 08, 2016 2:09 pm

Rainbows need not always appear to be very far away. On one particularly wet day in California, I saw a rainbow between my eyes and the far side of the road I was walking along.

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Re: APOD: Light Pillars over Alaska (2016 Feb 08)

Post by Ann » Mon Feb 08, 2016 2:17 pm

rstevenson wrote:A question for the experienced... Can you be surrounded by these sorts of light pillars? Or are they always in the distance, as rainbows are.

Rob
Light pillars in Stockholm, 2012.
Photo: Sam Hellerström.
I think you see them in the distance. We have these light pillars in Sweden too, occasionally (and you must have them in Canada sometimes, Rob), but fortunately for me (because they require such freezing conditions) I have never seen them or heard about them in southernmost Sweden, where I live. I know this kind of light pillars were seen in Stockholm some years ago, and the prestigious (and not so prestigious) Stockholm dailies proudly reported this glorious sight in the Stockholm skies. But they said nothing about anyone being surrounded by them.

Allisha, great picture! :D

Ann
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rstevenson
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Re: APOD: Light Pillars over Alaska (2016 Feb 08)

Post by rstevenson » Mon Feb 08, 2016 2:31 pm

Yes, Ann, somewhere in Canada we must have occasional light pillars. But here on the east coast we have a climate that is probably similar in some ways to southern Sweden. We'll never get ice crystals down close to street level here in Dartmouth. (I live about a 5-minute drive from the harbour, and 10 minutes from the open ocean.) I'd like to see them sometime.

Rob

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Re: APOD: Light Pillars over Alaska (2016 Feb 08)

Post by Chris Peterson » Mon Feb 08, 2016 3:00 pm

rstevenson wrote:A question for the experienced... Can you be surrounded by these sorts of light pillars? Or are they always in the distance, as rainbows are.
All you need are the right kind of ice crystals in the air and an unshielded light source nearby. If you have lots of those light sources around you, you'll see the pillars all around you. The problem is that the light sources themselves may wash out the pillars, so this looks best when the unshielded lights are invisible from your own location- blocked by low buildings or trees, for instance. A good place maybe to look for light pillars all around you might be in a small park in the middle of a town with poor lighting.
Chris

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Re: APOD: Light Pillars over Alaska (2016 Feb 08)

Post by BMAONE23 » Mon Feb 08, 2016 5:49 pm

This is what the effect might look like from directly below
Image
Here is the article
http://www.citylab.com/weather/2016/01/ ... ts/424287/

Uncle Norman

Re: APOD: Light Pillars over Alaska (2016 Feb 08)

Post by Uncle Norman » Mon Feb 08, 2016 6:41 pm

And aren't those noctilucent clouds in the background? Unrelated, I think, but cool to have both phenomena simultaneously.

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Re: APOD: Light Pillars over Alaska (2016 Feb 08)

Post by neufer » Mon Feb 08, 2016 7:47 pm

Uncle Norman wrote:
And aren't those noctilucent clouds in the background?
Unrelated, I think, but cool to have both phenomena simultaneously.
Noctilucent clouds or polar mesospheric clouds are primarily a summertime phenomena.

It's not dark enough to rule out normal tropospheric clouds...however:
https://en.wikipedia.org/wiki/Polar_stratospheric_cloud wrote:
<<Polar stratospheric clouds or PSCs, also known as nacreous clouds, are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 meters. They are best observed during civil twilight when the sun is between 1 and 6 degrees below the horizon. PSCs form at very low temperatures, below −78 °C. These temperatures can occur in the lower stratosphere in polar winter. In the Antarctic, temperatures below −88 °C frequently cause type II PSCs. Such low temperatures are rarer in the Arctic. In the Northern hemisphere, the generation of lee waves by mountains may locally cool the lower stratosphere and lead to the formation of PSCs.>>
Art Neuendorffer

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Re: APOD: Light Pillars over Alaska (2016 Feb 08)

Post by Boomer12k » Tue Feb 09, 2016 2:09 am

Another cool image of this phenomena...

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