The science behind the Aurora Borealis

Late August 2006. Fergus Falls, Minnesota. On a pristine Summer night, I witnessed the beauty of the Northern Lights dance in the horizon above Pelican Lake. One of the coolest moments in my life.

Courtesy: Bill Vaughn
Courtesy: Bill Vaughn

Last week, Facebook follower Bill Vaughn shared this photo of the Northern Lights (officially called the Aurora Borealis) in Fairbanks, Alaska. So what is the Aurora Borealis & why don’t we see it in Tucson?

It all starts with the sun. Occasionally, solar storms develop on the sun. These storms release highly charged particles, which are carried into the Earth’s atmosphere via the solar wind. Once entering the atmosphere, the particles collide with each other, setting off sky candy unlike any other.

AuroraBorealisGasColors

Depending on the gas in our atmosphere, the Northern Lights illuminate different colors. Nitrogen gas makes for the blue and green colors you see in Bill’s photo above, while oxygen touches off brilliant reds.

Why can’t we see it in the Old Pueblo? Thank the poles. The magnetic fields of the North & South Pole draw these charged particles toward them, making the Aurora Borealis visible at higher latitudes. There have been times when the Northern Lights were seen as far south as southern California, but it takes a very strong (and very rare) solar storm to produce a visible Aurora Borealis at lower latitudes.

Aurora viewing forecast map - courtesy Univ. of Alaska-Fairbanks (Note: this is not current)
Aurora viewing forecast map – courtesy Univ. of Alaska-Fairbanks (Note: this is not current)

The University of Alaska-Fairbanks has a site dedicated to where the Northern Lights will be visible from on a nightly basis. Above is an example of the maps they produce on their website. Click here for the Aurora forecast maps.

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