Monday, March 14, 2011

Light Pillar and Sub Sun

A light pillar is an optical phenomenon that occurs when the light of the sun reflects off tiny ice crystals floating in the air, forming a vertical column above the sun.

It usually happens when the sun is low in the sky, and sometimes even after it has set.


Light pillars can also occur near the light of the moon or streetlights, as long as ice crystals are floating in the air near you.

Ice crystals are often shaped like tiny flat hexagonal plates. Like falling leaves, they tend to float downward with the flat surface parallel to the ground.


Sometimes you can see a reflection of the sun off the top surface of these floating crystals. Looking down from an airplane window, a “sub sun” reflection will occasionally appear in a region below the horizon underneath the sun.

In the case of the magnificent photo above, the secondary light effect is a sub-parhelion, more rarely observed. It's caused by light that reflects off of the hexagonal internal surfaces of the ice crystals.  
Wikipedia on light pillar
Sub sun image from EPOD.
Nice explanation with diagrams of the ice crystals on Weather Doctor

6 comments:

Dalibor Dejanovic said...

James thanks for explaining about the light pillars! I never noticed one until this past January when I was outdoors painting. I dashed quickly to put it down on paper before disappeared. It is such a cool effect.

http://dalibordejanovic.blogspot.com/2011/01/happy-new-year.html

Prairie painter said...

I love this effect, which we call 'sun dogs' here. We get them in winter, and here is a link to a photo I took of smallish ones recently. BTW and loving your book and finding it so helpful and informative. Am going to blog about it as soon as I have finished.
http://www.flickr.com/photos/lorrainemk/5456661070/

Lorraine K

Sean said...

This is a cool effect. I don't know if I've ever payed attention to notice it in a sunset but definitely recognize it from street lamps like you said. I also just ordered your Light and Color book and can't wait for it to get here. I don't think I've stopped carrying around Imaginative Realism since I got it over a year ago. Your blog has been such an inspiration to me as well so I've started my own and have been doing it for a couple weeks now. I only post twice a week though. I would love for you to check it out and let me know what you think.

Thanks again,
Sean

Sean said...

Ha, sorry I forgot to leave the link, here it is...

http://seanssketchpad.blogspot.com/

agnespterry said...

Hi, just wanted to let you know my library told me that "Color and Light" is available for me to check out now due to my interlibrary loan request that I made a few weeks back! I am so excited! I can read it tomorrow. ( :-D --times triplicate.) So if people are dying to read it but there are no copies left in Amazon.com, they might consider this method.... Or if they are poor art students like me .....

Lana Klassen said...

The most dramatic example of light pillar I've ever seen was on a winter's night, when an oncoming train sent a beam like a searchlight up into the prairie sky. For a few moments, until I actually saw the train, all I could think of was UFO's!

Lana Klassen