KTUU.com | Alaska's news and information source | Hopes dim for aurora borealis displays this year

Hopes dim for aurora borealis displays this year

by Tracy Sinclare
Sunday, January 10, 2010

ANCHORAGE, Alaska -- Clear nighttime skies often mean a chance to see the aurora borealis, but this year the chances to do so are slim.

Named after the Roman goddess of dawn, the aurora never fails to capture our attention.

A space weather phenomenon, the aurora is caused by charged particles emitted from the sun. The Earth's magnetic field channels them toward the north and south poles, where they collide with the upper atmosphere. These energized particles get slowed down by collisions with atmospheric atoms and molecules, which causes light to be emitted in the colored bands that we see.

"The colors depend on which atom or molecule is doing the emission of light," said research professor Dirk Lummerzheim at the University of Alaska Geophysical Institute. "When the energetic particles come in they first collide with atomic oxygen, which is the lightest component of the air and is the highest up. And that gives us mostly the red color of the very high-altitude aurora."

As the particles penetrate deeper into the atmosphere they collide with molecular nitrogen, and the chemical reactions give us the green color we're so familiar with. Our eyes are more sensitive to green which is why we see more green in the sky, but cameras can pick up that high red band.

But when there's little solar activity, there's not much for us to see here -- and that's what we can expect for this winter.

"The sun goes through an 11-year cycle, having activity that rises in magnitude and then eventually dies down and gets very quiet every 11 years," Lummerzheim said. "We are currently in one of those minima that occur every 11 years, and that is the reason that we have so little aurora here as well."

The short-term forecast for the aurora is done by watching the sun -- a solar flare directed toward the Earth will result in an aurora two to three days later. But the long-term forecast is based on the rise and fall of overall solar activity, which is important when your job is taking pictures of the Northern Lights.

"We are coming into the new cycle," said aurora photographer Todd Salat. "I think the bend has been made out of deep solar minimum into the next solar cycle, and the next couple few years are supposed to get better and better and better, and maybe peak around 2013 or so."

Salat routinely checks the forecast, but finds that sometimes you just have to keep an eye on the sky and take a chance.

"Last night was a perfect example," Salat said. "I did not expect to see the Northern Lights. I was just going to go out, the forecast was for quiet skies. And there I sat at 11:30 p.m., and all of a sudden a green band came in -- and by midnight, they were dancing."

Even scientists say finding the aurora takes more than just science.

"I mean, you can make computer models of the aurora and convince yourself that you tend to understand what's going on up there," Lummerzheim said. "And all you need to do is step out on your porch and look up, and convince yourself you don't understand a thing of what's going on in there."

Contact Tracy Sinclare at tsinclare@ktuu.com