The color and variety of northern lights can vary from intense undulating greens, like here at Jay Cooke State Park in Minnesota, to tones of orange and red to streaks of purple among the green.
The fire tower was silhouetted by a red glow in the western sky. But it was not a fire illuminating the November night; it was one of the most spectacular displays of the aurora borealis (northern lights) that the Lake Superior region had seen in years. The date was November 7, 2004. The event that night was noted from California to Quebec, from Alaska to Arizona.
We pulled the car over and stood under a dome of flowing color. Not only in the north, the aurora wrapped around us to the east, south and west. Pulsing white bands turned into rippling green curtains that morphed into red streams. It seemed that there should be sound; swooshing and static as lights meld and move. But the night was silent and we stood in awe. Suddenly, a corona formed overhead. We could hardly believe our eyes; this is an extremely rare event south of the Arctic Circle. A corona is the epicenter of an auroral curtain and we were directly beneath it, looking into a ring of green and red light. Reds, greens, purples painted the skies. Sunspot 636 was the culprit as it spewed strong solar flares toward earth, including a powerful X-1 flare (the highest magnitude), which triggered a massive geomagnetic storm as the energy hit the earth’s magnetic field. Aurora alerts had predicted the event, but no one had foreseen how widespread it would be. It would even ignite the aurora australis over New Zealand.
Most commonly people see the “Is-that-the-Northern-Lights? No-can’t-be. Well-maybe-it-is” version of the aurora. This form is a pale arc of whitish or greenish light appearing low in the northern horizon.
For us in the Lake Superior region, the more impressive display with rippling green curtains of light is not rare – there are advantages to living Up North. But auroral displays happen every minute of every day – 24/7, 365 – along the auroral rings near the north and south magnetic poles. In Churchill, Manitoba, on Hudson Bay, you can see northern lights virtually every clear dark night.
Every culture in the aurora belt has created its logical explanation for unexplained heavenly happenings. Inuit hunters believed that the flowing glow revealed dead ancestors kicking around a walrus skull in the afterworld. Inuk shamans regularly visited the moon and the northern lights. These “spirit journeys” were to visit departed relatives.
Scandinavia has many legends relating to the lights. Revontulet is the Finnish name for the aurora. It was believed that foxes made of fire stalked the Lapland wilds. One whisk of a tail sent red light skyward. Norwegian sailors believed that light reflecting off massive schools of herring caused the shimmer in the sky. The Vikings rarely mentioned the nordrljós (old Norse for “north light”), but in 1250 A.D., in the book Konungs Skuggsjá (The King’s Mirror), a Viking scholar put forth the three commonly held explanations: Fires that ring the northern oceans lend light to the sky; sunlight slips into the night sky when the sun moves beneath the earth; or the lights emanate from frost and growing glaciers beyond the curved horizon. But he sagely concluded, “as to their correctness, I do not decide.”
Closer to Lake Superior, Ojibway people understand northern lights as the departing or the dancing of brightly clothed souls.
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The aurora borealis over Wauswaugoning Bay, Minnesota.
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The aurora borealis over Wauswaugoning Bay, Minnesota.
It helps to know something about plasma physics to understand the formation of the aurora … and I don’t. But I’ll give it a shot here anyway. The very simple explanation is that northern lights result from electrons that collide with atoms in the upper atmosphere and give off their energy as light.
Now the long and complicated version:
Sunspot activity and solar flares catapult solar winds of hot plasma (gas of free electrons and positive ions) toward earth. As Candace Savage explains in Aurora: The Mysterious Northern Lights: “As the sun rages and storms, it spews out a continuous stream of plasma – a thin, electrically neutral spray of charged particles. A gusty blustery outpouring of both matter and energy, this ‘solar wind’ blasts through space at speeds of 1 million to 3 million kilometers per hour.”
This killer blast is deflected by our magnetic field a mere three minutes before wiping out all living things on earth. Since the sun is magnetic like the earth, the plasma is embedded with a magnetic blueprint. If solar magnetism is sent in a certain direction, massive amounts of energy are sucked into the earth’s magnetosphere and the auroral belts (rings around the magnetic poles at extreme northern and southern latitudes). Gusts of plasma blow over the fused magnetic fields of sun and earth, creating electrical power. High-speed electrons bombard the thin gas of the upper atmosphere (ionosphere). When they collide with atomic oxygen, the oxygen atoms become agitated and absorb some electron energy, then give off that familiar green glow.
Red-sky auroras are quite rare and occur only during major bombardments of our atmosphere. High in the ionosphere (higher than 120 miles up), where the air is very thin, collisions between oxygen atoms and electrons knocked from other atoms create energy as red light. But the atom must keep the charge for nearly two minutes for the glow to form. The waving curtains, coronas, streaming bands and other northern light incarnations are actually movements of the magnetosphere’s electron beams made visible by the light they create.
Northern lights normally occur in the “auroral oval,” a band around the earth’s magnetic North Pole. The oval varies in width but is centered over Hudson Bay, the interior of Alaska, northern Siberia, Iceland, Tromso in Norway, southern Greenland and Labrador. The lights are rarely seen at the geographic North Pole and middle latitudes. But the ring is more active in some areas than others, and it does expand and contract based on the solar wind. It takes a strong geomagnetic storm for lights to be seen in the central United States. The aurora australis – southerly cousin of the northern lights – can be seen in an auroral ring around Antarctica, occasionally visible in Australia and New Zealand.
Fortunately there is still mystery left in the northern night; science can attempt to unravel their intricacies for years to come.
But on that chilly November night, as we stood beneath a dome of mesmerizing motion and color, we could have cared less about plasma physics.
The primal thrill was all that mattered.
Purple-tinged northern lights at Hollow Rock Resort in Grand Portage, Minnesota.
Increase Your Odds
If you really, really, really want to witness the aurora borealis, it would probably be best to rent a cabin for a month near Churchill, Manitoba, or in the interior of Alaska in midwinter. Then look up frequently.
If you don’t have that kind of time, money or tolerance for cold, here are tips to tip the scale in your northern-light spotting favor.
Concentrate on winter: Northern lights occur year-round, but who’s up at 2 a.m. to search the skies?
Look north: They ain’t called the northern lights for nothing.
Get out of town: Many cities, towns and villages are “polluted” by light. Street lights, billboard illumination and security lights all add up to a sky-shielding haze.
Be alerted: Many websites send notices or even phone calls to subscribers about especially heavy solar flare activity.
Sparky Stensaas is a naturalist, writer and photographer based in northern Minnesota.