Few things reward life in a northern clime like catching a glimpse of the aurora borealis -- a mirror image of the southern aurora, the aurora australis, that's taking place at the same time. If you've been lucky enough to see the northern lights, you understand that hardly anyone can turn their back on them once they appear. It's just too easy to while away the minutes, lying in the snow or perched on the hood of your car, watching the lights.
As beautiful and ethereal as the lights are, they're actually created by a simple reaction -- the electrical charges that happen when gaseous discharges from the sun collide with the earth's atmosphere. Basically, the aurora is a neon light set free from its tube to dance across the sky. But not every discharge that leaves the sun will actually hit the Earth, much less result in an aurora.
The science
For starters, the gas discharge -- known as a coronal mass ejection or CME -- has to come out of the right part of the sun (near its equator), and must be aimed far enough ahead of the Earth to hit us when it finally arrives, two days later. (Remember, the Earth is in constant motion around the sun.)
Once the gas does leave the sun, "The storm, as it leaves the sun, is like a tumbleweed... it's rolling and twisting, and gets bigger and bigger as it gets farther from the sun. It carries its own little magnetic field from the sun, but it's always twisting and turning," said Neal Brown, a geophysicist and educator who studies the aurora borealis.
Brown explained that if the side of the tumbleweed that contacts the earth is positively charged it'll bounce off the Earth's magnetic field, like what happens when you hold two magnets with both positive or both negative poles together. No aurora. But if the negatively charged side hits the Earth, it "sticks" and transmits the energy to create an aurora.
Unfortunately, there's really no way to forecast aurora far in advance. We only know they're coming when spacecraft positioned between the sun and the Earth detect a CME. That works out to a day or two of lead time, or as little as a few hours if you really want an accurate prediction.
One useful tidbit scientists do know, however, is that it takes 27 days for an active area on the sun to line up with the earth again -- so if you see a good aurora, Brown said, it's very likely that 27 days later will be a good time to look again.
Can you see me now?
Massive CMEs aside, your next best indicator of the aurora is the Kp level, which professional photographer and "aurora hunter" Todd Salat likens to the Richter scale for earthquakes.
The higher the Kp level, the greater your chances of seeing the aurora. In a phone interview, Salat explained that where you live also determines where you should look to see the lights. Aurora-watchers in cities farther north, like Fairbanks, can often just look up. But for those in Anchorage and lower latitudes, you're more likely to see the aurora along the northern horizon.
That means the best vantage points around Anchorage will be high up, with a good view to the north and relatively little light pollution -- Salat recommends the Glen Alps parking lot and, depending on how adventurous you're feeling, the overlook trails around it. If you want to head north you could try going up Skyline Drive in Eagle River ("I understand it gets pretty crowded up there," Salat said) or Hiland Road. If you're heading south, he says, the trick is finding a bend in the highway that gives you a view toward the north -- sometimes easier said than done, given how the road twists and winds around the mountains.
Mind your midnight manners
When I asked Salat about aurora-viewing etiquette, he only had one big point to make: "It's all about the light." Your car's headlights are one of the best opportunities for building a little good karma: "If you feel comfortable turning your headlights down to dims, and then if you can see good enough, try just going with your running lights once you're in the parking lot and creeping along really slowly," Salat said.
And if you're idling your parked car while you wait to see aurora, definitely keep your headlights off. You might even rethink leaving it running if others are watching nearby, since the exhaust could interfere with their view.
Headlamps are useful tools for seeing what you're doing, especially if they have a red-light mode so they don't destroy your -- or anyone else's -- night vision. Salat was pretty low-key about the possibility of offending someone with a headlamp, but as someone who's been beamed on the trail many a time, I'll go there -- keep it on the lowest setting that's useful to you, and make sure you're not shining it in anyone else's eyes (or camera).
Photographing the aurora
Salat has three tips for the everyday photographer: "You have to have a tripod, even if it's a cheap one. Then, with whatever camera you have, you have to figure out how to make it do a longer exposure... at least a couple of seconds."
Finally, put your camera on a short self-timer delay (Salat recommends about two seconds) so that your hands won't jiggle it during the exposure time; this gives you a much sharper image. If you get a photo that's too dark, use a longer exposure; if it's too bright, use a shorter exposure time.
As for the unexpected challenges of aurora hunting, Salat says one of the biggest is maintaining an inverted schedule so you can be awake at night to see the aurora. If you can be up, he says, use your hand to block out the streetlights (if you have them) and look for a green band to the north as often as possible, about every 15 minutes or so. Then wait for the band to melt into a grandiose light display.
If you can't keep late hours, don't despair; Salat says the early-morning hours before work are another chance to see the aurora, especially the magenta and purple colors that often occur right before sunrise.
All the gas giant planets in our solar system have auroras too, but it's Earth that has the oxygen and nitrogen in the atmosphere to create beautiful blues, greens and reds -- and the people here to see it. Though they've pursued the northern lights for years, it's obvious that Salat's and Brown's enthusiasm has never waned.
"I think the aurora is an amazing thing... it's the most beautiful show in the universe as far as human beings are concerned," Brown said.