I saw the northern lights for the first time in 1990. A friend and I were driving through Wyoming on a frigid February night when I looked out the window of our truck and saw...it. Eerie green fingers seemed to be streaming from the sky directly above us. Then, suddenly, the whole sky began to glow and undulate. Stunned, we pulled over to the side of the interstate to check it out. The lights were so awesome that we both climbed out of the truck - where the heater was cranking to the point that we were comfortable in T-shirts and shorts - and stood, barefoot and slack-jawed, in the snow, staring silently at the spectacle overhead.
The northern lights are like that. Once you've seen them, you never forget it, and you spend the rest of your life looking up at the night sky hoping to see them again. If you haven't seen them, you don't know what you've been missing.
I guess a major part of the allure of the aurora is that for most us who live in the U.S., a glimpse of the northern lights may well be a once in a lifetime experience. Unless you're in Alaska, where the aurora is pretty much a standard feature of the winter sky, or the northernmost latitudes of the "lower 48", the odds are strongly against you seeing the northern lights. The auroras - yes, there are southern lights, too, known as the Aurora Australius - occur around the north and south poles in auroral ovals, where the earth's magnetic fields interact with the solar wind. The farther you are from the poles, the worse your chances of seeing an aurora.
Without getting too technical, the auroras are created by the atmosphere glowing as the charged particles of the solar wind stream along the earth's magnetic field lines. The auroras stretch throughout the upper limits of the atmosphere, stretching from about 40 miles above the earth to around 600 miles up. (So there's no way anybody's plane ever flew through the northern lights, no matter what they tell you.) As the electrical energy created by the solar wind passes through the various bands of atmospheric gasses, those gasses glow different colors, and you have an aurora. As a bonus, you can actually get a fairly good idea of how high up the aurora is by what color(s) you're seeing. The oxygen at 60 miles or so above the earth glows bright yellow-green, and is probably the most commonly seen auroral tint. If you're quite lucky, you'll get a look at an all-red aurora, the result of high-altitude oxygen glowing about 200 miles overhead. More likely, you'll see a yellow-green aurora with maybe some blue from ionized nitrogen or a little red from neutral nitrogen, both usually seen around the auroral edges or ripples.
Since the solar wind and the earth's magnetic field are permanent features of the upper atmosphere, so is the aurora. That's why the folks in Alaska and northern Canada get year-round auroral activity. For the rest of us, seeing the northern lights takes some planning.
The auroral oval, where the northern lights can be seen, isn't a static area. The oval can be a few hundred miles wide, or more than 1000 miles thick, depending primarily upon the amount and intensity of solar wind. Generally speaking, the solar wind is determined by the amount of solar activity, which can be tracked by watching the amount of visible sunspots. The more sunspots, the more solar activity; the more solar activity, the more widely visible and more spectacular the auroral display.
Now, predicting solar weather is a long way from an exact science, but we do know that sunspot activity is cyclical, peaking every 11 years or so, which gives us some clue as to when to be on the lookout for the best auroras. And as luck would have it, the next peak in solar/auroral activity is expected to take place - when else? - in the year 2000. How's that for a harbinger of something or other?
I don't go in much for apocalyptic notions, but I am looking forward to getting myself into position for as much auroral viewing as possible over the next couple of years, and you can easily do the same. First off, remember that the further north you can get, the better the viewing. Also, since the aurora is a body of light, it's usually only visible at night, so the more hours of darkness, the more you'll see the aurora, so plan on doing at least some winter viewing to take advantage of the long nights. Bonus factors - the aurora is perfectly visible to the naked eye, so you don't need to bring your binoculars or telescopes out, and it lasts long enough to make photographing the event a piece of cake. You will need a tripod and a camera capable of timed-exposure shots, but nothing more.
If you're really serious about seeing the aurora, like I am, and you have Internet access, the University of Alaska Geophysical Institute has a web page with updated daily aurora forecasts for the entire northwestern hemisphere. The Institute's website also has weekly forecasts, so you can plan that trip to Michigan's Upper Peninsula accordingly.
I'll see you there. I'll be the barefoot guy by the side of the road, staring up in wonder.
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