Look Up!

Kristen Lindquist: Understanding the Aurora Borealis

Posted:  Tuesday, November 22, 2016 - 1:45pm
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Late at night sometime in early spring 1989, at Middlebury College in Vermont, word spread quickly through the dorms: Go outside and look at the sky! Northern Lights!

Most of us were still awake. I put down my books, donned my warmest parka, and joined the crowd heading outside. Despite the hour and the frigid temperature, hundreds of students were hanging out on the greens, heads tilted upward. Across the night sky's black backdrop, bright sheets of green light shifted, danced, and swayed: the northern lights, aurora borealis. My hilltop dorm was on the campus's highest point. Viewed from there, the waves of light seemed to sweep down over our heads, shimmering, translucent curtains fluttering just out of reach.

Many students had never seen the aurora before. All were in awe. This strange and beautiful phenomenon had drawn us outside to the night sky's very own party, into an atmosphere charged with late-night giddiness and rock concert fervor. This was a magic show of the highest order. For me, about to graduate in a few months, it felt like a good omen for my uncertain future.

A natural phenomenon so strange, unpredictable, and breath-taking as the aurora borealis has long been the stuff of omens and legends around the world, even in places that may never see the northern lights. The name aurora comes from the Roman goddess of dawn, presumably for the light in the darkness; borealis comes from Boreas, the ancient Greek personification of the north wind, which pegs their viewing location as North. The Greeks and Romans would have seen the Northern Lights very, very rarely. (The same phenomenon around the South Pole is called aurora australis, the southern lights.)

Among the Chinese and Japanese the belief that a child conceived under the northern lights will be especially beautiful and fortunate had led to a rise in aurora-related tourism in places such as Tromsø, Norway. According to Icelandic folklore, childbirth itself will go smoothly during an aurora manifestation. On the other hand, natives of eastern Greenland believed the lights were the dancing spirits of stillborn babies. In fact, many cultures, such as the Kwakiutl and Tlingit of Alaska, equated the northern lights with restless spirits of the dead.

Spirits of the dead are, of course, to be respected. The Sami people of northern Finland traditionally responded to a display of northern lights by staying inside and lowering their voices. Whistling was a no-no that might lead to your being carried off by the lights. Flying Dust First Nation people in Saskatchewan tell a morality tale about a bratty young boy who whistled at the aurora spirits after being explicitly told not to. His grandfather was able to keep the spirits from immediately carrying off his grandson, but three months later, the boy died.

Some Inuit saw them as the spirits of animals they had hunted. Many other Inuit peoples regarded them as spirits of the dead playing a soccer-like game using a walrus skull as the ball. Interestingly, a Penobscot story from Maine also associates the aurora borealis with a ball game: Chief Morning Star's only son would often head north and disappear for long periods of time. Following his son, the chief traveled via the Milky Way to a strange place, "the country of Wa-ba-ban of the northern lights." There he found his son playing a ball game in which all the players wore lights on their heads and "rainbow belts"; the chief's son wore the brightest light of all.

The Fox of Wisconsin saw the lights as their slain enemies agitating for revenge; when they appeared in the sky, war was on the way. If the lights are red, be especially wary of war. The aurora apparently glowed red in northern England and Scotland shortly before the French Revolution.

The Menominee saw them as torches carried by benevolent giants while spear-fishing at night. Fishermen in northern Sweden believed that seeing the aurora was a sign that large schools of fish awaited. There is certainly something reminiscent of the play of water over fish scales in the aurora's shimmer. For the Anishinaabe people, the celestial lights come from large fires lit by their cultural hero Nanabozho, who moved far away to the north after creating the world and kindly wants them to know he's still thinking of them.

The scientific explanation for the northern lights is more prosaic. When charged particles from the sun blown by solar winds collide with the earth's upper atmosphere, the earth's magnetic field deflects these particles toward the two poles. At the poles they interact with atmospheric gases to produce fantastic arcs, bands, rays, and waves of light. The physical process is similar to that which produces neon light. Aurora displays are most commonly or predominately green, a result of ionized oxygen in the lower atmosphere, but can also be red, yellow, and blue depending on what other gases are fired up.

The light show happens from 50 to more than 300 miles above the earth, and within a donut-shaped space centered on the poles. Because geographic north is not the same as magnetic north, the optimal viewing area is not centered on the North Pole. But generally, the Northern Lights are visible for much of the year — when night skies are clear and the moon isn't too bright — from 60 to 75 degrees latitude.

Maine is obviously south of that, so for us they are a relatively unusual phenomenon, dependent on the stronger solar storms and flare-ups that create larger displays. A fairly regular 11-year solar cycle helps predict periods of greater solar activity that may lead to more extensive northern lights. Unfortunately, we are on the waning end of a solar cycle that began in 2008 and which has been one of the least active cycles of the past century.

The National Oceanic and Atmospheric Administration (NOAA) offers three-day predictions for aurora displays at www.swpc.noaa.gov/node/114, based on a measurement of solar emissions called the Kp index. Here in Maine the Kp Index needs to be Kp 6 - 7 or higher for us to have a shot at seeing the aurora.

You can check in with NOAA throughout the winter to see if this spectacular light show — so wrapped in fascinating myths and legends — is coming soon to a sky near you. And you can also sign up to receive email updates on solar activity from spaceweather.com that share things like:

SUN HURLS PLASMA CLOUD TOWARD EARTH. Yesterday, Nov. 5th, a magnetic filament on the sun became unstable and erupted. The blast opened a fiery canyon in the sun's atmosphere and hurled a CME toward Earth. According to NOAA models, the plasma cloud could strike Earth's magnetic field on Nov. 8th, triggering G1-class geomagnetic storms and auroras around the poles.

Get hooked on that kind of excitement and before too long, you're going to find yourself researching northern lights tours to Norway along with all those Japanese newlyweds!