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Aurora borealis FAQs

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Posted: Friday, May 4, 2012 11:31 am | Updated: 2:58 pm, Mon Mar 4, 2013.

FAIRBANKS - The brilliant, vibrant and lively colors that dance across the northern skies inspire wonder in the hearts and minds of even the most hardened longtime Alaskans. The aurora borealis, or the northern lights as they are also commonly called, are a sight to behold, and one of the many wonders of the Arctic.

A reliable local source of information regarding the phenomenon is the University of Alaska Geophysical Institute, which provides a wealth of information, an aurora forecast and a place to sign up for aurora alerts. Visit www.gedds.alaska.edu/auroraforecast. The Geophysical Institute provided answers to some common aurora questions:

Q: What is the aurora?

A: The luminous glow in the sky, called aurora, is the result of energetic particles entering the upper atmosphere.

This specific glow is different than other forms of brightness in the sky, such as scattered sunlight or lightning. Magnetism within the Earth’s atmosphere guide the energetic particles, most often electrons, along field lines to the high-latitude atmosphere. As they penetrate the upper atmosphere, the chance of colliding with an atom or molecule increases the deeper they go. When a collision occurs, the atom or molecule takes some of the energy of the energetic particle and stores it as internal energy while the electron continues on its path at a reduced speed. The release of that stored energy by an atom or molecule, achieved by sending off a photon, produces light. 

Q: What makes the color in the aurora?

A: The composition and density of the atmosphere and the altitude of the aurora determine the possible light emissions.

The atmosphere is made up of varying levels of oxygen and nitrogen. Sometimes the photos emitted by the energetic electrons, creating aurora energy, are strong enough to split the molecules of the air around them into oxygen and nitrogen molecules and atoms. This process gives them the signature colors of nitrogen and oxygen atoms. Oxygen atoms typically emit green and red colors.

The overall impression is a greenish-whitish glow. Very intense aurora can get a purple edge at the bottom, which is a mixture of blue and red emissions from nitrogen molecules.

Q: What is the altitude of the aurora?

The bottom edge is typically at 60 miles altitude, but it extends over a large altitude range. Very intense aurora from high energy electrons can be as low as 50 miles.

The top of the visible aurora peters out around 120-200 miles but sometimes high-altitude aurora can be seen as high as 350 miles.

 Q: How often is there aurora?

A: There is always some aurora at some place on Earth. You just can’t always see it.

When the solar wind is calm, the aurora might be too high and faint to see.

In order to see aurora, the sky must be dark and clear, which means in the land of the midnight sun, the phenomenon is invisible during the bright summer months.

Summer visitors should not despair: Local photographer LeRoy Zimmerman spent much of his career documenting the aurora at its best from desirable locations throughout the state.

He has created the world’s only panoramic wide screen aurora performance, all set it to symphonic music. He has offered the auroral experience to audiences since 1984.

“It’s the only award winning, and the longest running, original aurora show in Alaska,” Zimmerman said of the spectacle, which he calls a photosymphony.

He displayed his show at the Ester Gold Camp for more than 20 years, took a one-year hiatus when the camp closed, and restarted the show, in digital form, at the Lacey Street Theatre in 2009.

Zimmerman said Photosymphony does more than offer the visual beauty of the aurora in the pictoral display; the classical symphony music helps create an emotional response, Zimmerman said.

“You can see the aurora (in many pictures) but what I am trying to do is to help you feel it. That is what you can’t put into words or capture with a picture alone,” he said.

Photosymphony runs every day at 8 p.m. in the Lacey Street Theatre.

Information is available at www.photosymphony.com.

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