Chasing the aurora

Northern lights seekers take advantage of solar activity and clear winter nights

Posted: Sunday, January 26, 2003

Chicago-raised Michael Orelove remembers the first time he saw the northern lights after moving to Alaska.

"It was just amazing," said Orelove, a Juneau stargazer and Marie Drake Planetarium volunteer. "Pictures do not do it justice because it does completely fill the whole sky. You have to turn your head to see the show."

When the skies are clear and conditions are right, Orelove and hundreds of others head out into the cold, often windy night in search of the aurora borealis.

They gather along roadsides, on frozen muskeg bogs and on wave-washed beaches away from urban lights to watch the magnetically driven illuminations form lines and curtains that wave and dance across the sky.

But the time for watching the aurora, at least in Juneau, is growing short. We're on the down side of an 11-year cycle of the sunspots and solar flares that power the lights.

"It's relatively quiet right now," said Charles Deehr, an auroral forecaster at the University of Alaska Fairbanks Geophysical Institute.

"We're expecting them to fall off considerably as the solar activity falls off at the end of 2003," said Deehr. "This spring should be a good time to see the aurora, especially in the new moon periods in February, March and April."

The lights we call the aurora borealis are caused when solar wind, boosted by sunspots and flares, interacts with the Earth's magnetic field to charge up atoms and molecules in upper atmosphere. Starting 50 or more miles above the surface, the lights form a ring around the north - and the south, where it's called aurora australis.

Web links

For more on the aurora, check out these Web sites:

• University of Alaska Fairbanks Geophysical Institute, including the daily aurora forecast.

• Aurora for kids

• Auroral picture gallery, a private collection assembled in Fairbanks

• Mid-latitude aurora-watch, a Boulder, Colo.,-based site including a photo how-to section.

• Michigan Tech aurora page

The aurora is going just about all the time, somewhere, but only can be seen when clouds don't block the sky, competing light from the sun, the moon and human-made illumination is at a minimum and the atmospheric interaction is intense.

Scientists predict auroral activity by monitoring the sun's surface.

"A solar event will occur and we have about three days to get ready for it. It takes about that long for the shock wave to reach the Earth," said Deehr. "We had the first flares on the 20th, the first ones for a month. Previously during this cycle of sunspot activity we were having one ever three days. Now it's a month so it's definitely falling off."

Juneau residents most often see a green or yellow-green aurora, produced by oxygen atoms at roughly 60 miles up. According to Neal Brown, senior consultant at the Geophysical Institute, rarer red auroras come from oxygen atoms as high as 200 miles above the earth's surface. Ionized nitrogen molecules produce blue light while neutral nitrogen molecules create purplish-red lower borders and ripple edges, according to Brown's Web site.

The colors of the lights

Auroras are similar to color television images. In the picture tube, a beam of electrons controlled by electric and magnetic fields strikes the screen, making it glow in colors that vary with the screen's phosphor. Auroral color depends on the type of atoms and molecules struck by the energetic particles, particularly electrons, that rain down along earth's magnetic field lines in the discharge process. Each atmospheric gas glows with a specific color, depending on whether it is ionized or neutral, and on the energy of the particle hitting the atoms and air molecules.

The brightest and most common auroral color, a brilliant yellow-green, is produced by oxygen atoms at roughly 60 miles altitude. High-altitude oxygen atoms (about 200 miles) produce rare, all-red auroras. Ionized nitrogen molecules produce blue light; neutral nitrogen molecules create purplish-red lower borders and ripple edges.

- from "The Aurora Explained," by Neal Brown

Many northern light chasers turn to the Internet to know when to go out looking. A popular site is the Geophysical Institute's aurora forecast Web page, which includes a map showing where the lights are most likely to be seen overhead and on the horizon.

The forecast showed Juneau in, or at the southern edge, of the horizon visibility area for most of the past two weeks. Saturday's forecast, however, showed the area shrinking, with Juneau left outside the likely viewing area.

When the prospects are good, Juneau aurora-watcher Orelove lives downtown, where mountains and city lights can diminish the view.

"I go across the bridge to Douglas and Sandy Beach and look back over Mount Roberts," he said.

Steve Kocsis, another planetarium volunteer, said last week's clear skies and good forecast sent him outside.

"I live in the Valley so usually I view them from the glacier visitor center bus parking lot," he said.

Hiker and kayaker Larry Musarra often spots the aurora out the window of his North Douglas home. Then he grabs his camera and heads to a level stretch a short distance up the road to Eaglecrest that offers a broad, unobstructed view.

"It's a nice east-west horizon that gives you a really good shot to the north," he said. "The whole sky from all the way up to Tee Harbor and down to the Taku, it's pretty well lit up."

Outdoorsman and Trail Mix director James King likes to check out the lights from Eagle Beach.

"If the tide isn't high you can walk out on the beach and watch. It's really fantastic," he said. "The challenge is when the northern lights are out it's usually cold and windy."

While Juneau still has a few months of potentially good auroral activity, the decline in sunspots and solar flares will lower the number of viewing opportunities over the next few years. Those looking for overhead light shows might consider a trip north, said Deehr.

"If you want to see the northern lights, you should come to Fairbanks during March in the new moon," he said. "You're pretty much guaranteed to see the aurora."

Ed Schoenfeld can be reached at eschoenfeld@juneauempire.com.



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