Lee Sacrey Photography – Lee's Chatter

Mainly Photography but a little of everything at times

Aurora Borealis- What are the Northern Lights?

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Living in Yellowknife, Northwest Territories, Canada gives me a great number of opportunities to see and photograph the Aurora. This week has been a good one for Aurora viewing. While I was out this week I was thinking about “Do most people know what the Northern Lights really are?” I thought I would give a little information on them and post a few pictures from this weeks shooting.

I guess I will start by saying there are actually northern and southern lights. Both are Aurora, the northern ones being call Aurora Borealis and the southern being called Aurora Australis. My focus will be on the northern Aurora. The term Aurora Borealis was first used by Pierre Gassendi in 1621. It comes from Aurora, the Roman goddess of dawn and Boreas, the Greek name for the north wind. They were called “Dances of the Spirits” by the Cree Indians. The closer you are to the magnetic north pole the easier the Northern Lights are to see (which is why Yellowknife is one of the best places on Earth to see them). They normally occur in the ionosphere, which is generally 50 miles (80 kilometres) above the Earth. They occur more frequently close to the equinoxes.

What happens is, the solar winds are funneled down and speed up along the Earth magnetic field lines. Those solar winds collide with oxygen and nitrogen atoms which excites them. When moving from an excited state to a grounded state those atoms emit photons. So, ions generally flow outward from the sun, they are gathered up by the solar winds and as they move toward the poles they are accelerated towards Earth and collide with atoms. These collisions causes the excited energy to be released by the emission of photons of light. These photons of light become what we see as the Aurora Borealis or Northern Lights.

The different colours are created by the different types of emissions. Oxygen emissions are green or brownish-red and nitrogen are blue and red. Usually red lights happen higher in the atmosphere as collisions don’t happen as often there and it takes longer for oxygen emissions to emit the red colour. Because collisions happen more often in the lower atmosphere where the time between collisions is shorter we generally see green lights, as they (emissions) have less time to produce coloured light. When nitrogen emissions happen we usually don’t see any of the usually green and brownish-red lights as the nitrogen prevents the oxygen from emitting anything.

So, there it is my readers digest or Coles Notes version of what the Aurora Borealis are. If you want some more information, I am sure a quick online search will find you a wealth of information. I hope this helps explain a little about why we see these beautiful lights. If you are in Yellowknife and want to see some nice Aurora images, I suggest you head down to the Snow King’s Castle. There you can find Karl Johnston and some of his Photographs, he has some very cool stuff, I picked up a small print myself there today. If you want to see what I saw this week here is a sample and as always, thanks for looking and Happy Shooting.

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Written by leesacrey

March 20, 2010 at 5:21 PM

3 Responses

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  1. Amazing shots Lee! I love your aurora work. In particular the lines in #1 and #5 – really striking.

    Out of curiosity, do you havbe any tips for reducing noise in longer night exposures?

    Mike

    March 22, 2010 at 12:19 PM

    • Hey Mike, good to here from you once again. Before I answer your question I should tell you I reworked that photo you mentioned in your last post and it looks great. Thanks for the critique. Now for this question, the interesting thing about my night shots are that I actually turn my noise reduction off. My long exposure reduction is turned to normal. So, you would think I would get more noise but, I leave the ISO really low. On my a700 I set the ISO to 200 and shoot 1 to 2.5 minutes. The low ISO produces low noise so, noise reduction is not really needed. It also speeds up the time it takes to process the image. I would like to take credit myself for figuring this out but, Darwin Wiggett actually suggest I try it after we were looking at some images I did at ISO 1600. Sometimes I have auto ISO turned on and I can set a range for my cameras auto ISO setting. I have it set to go between 100 and 400 only. So, I would say to try a low ISO first and see if it works for you.

      leesacrey

      March 22, 2010 at 5:21 PM

  2. Hi there,I like going through your blog, I want to to leave a little comment to support you and wish you a good continuation. Wishing you the all the best for all your blogging efforts.


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