Tuesday, August 3, 2010

A Rare Opportunity to See Auroras

This week there is a rare opportunity for people living in the northern regions of the US to see the spectacular light show, aurora borealis. (Those living toward the South Pole, particularly in New Zealand and southern Australia, may likewise have the chance to see the aurora australis.)

Typically, we see these curtains and arcs of light near the winter and spring equinoxes, when the air is less dense and the weather is clear. The closer you are to the poles, the more likely your chance of getting a viewing. But this week, people living in the northern regions of the US, from Maine to Michigan, and in Canada should have the opportunity to see a pretty exciting summer light show out of season, courtesy of Mother Nature.

This opportunity is the result of a series of sun storms that flared on Sunday. The storms have sent waves of plasma toward earth, which should arrive late Tuesday night and into Wednesday. This plasma is not anything to be concerned about -- it is what we call "solar wind" and is simply a gas of free electrons and positive ions. These electrons and ions enter earth's atmosphere and begin the process of colliding with oxygen and nitrogen atoms, creating a geomagnetic storm.

The color visible in the sky is dependent on the interaction. The ionization and excitation of oxygen atoms tends to produce brownish-red and green waves of light; nitrogen tends to create blue or red. (For more on the ionization process, see our module Atomic Theory II.) The best chance you'll have of seeing the lights is to get as far away from human light sources, like cities, and into the countryside. The map on the right, courtesy of the NOAA Space Weather Prediction Center, gives an idea of who is most likely to be able to see the aurora as it occurs.

If you have an opportunity to see the show, please let us know what it was like! Even better, share your photos!

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