| Author: |
Abigail B. Calkin |
| Dated: |
Wednesday, April 15 2009 @ 04:00 PM EDT |
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1340 times |
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In autumn, winter, and spring, the aurora dances reds, greens, yellows, whites and blues across the heavens.
If you have never seen an aurora, imagine a rainbow. To intensify it, backdrop the rainbow against a black sky. Look at the colors. Now start undulating it in separate waves or flashes that snake or whip across the sky. Imagine a colored glow that changes the sky from its darkness to green or white or, if you're very lucky, the crimson red of a sunset or rise.
Some Alaskan Natives believe that if you whistle, the lights will come down to get you. Another legend says that they are the spirits of those who have died and reached the highest level of heaven, the level where there is no snow and only brightness. There are some common circumpolar traditions shared by the natives of those areas—Eskimo of Alaska, Inuit of Canada and Greenland, Sami of Scandinavia and Russia—that the lights are the spirits of those who died a violent death of childbirth, suicide, or murder; it is their blood that makes the aurora. Others say the movement represents spirits playing ball. Some cultures say the northern lights are a game of soccer with a walrus head, complete with tusks. According to one European legend, battles were fought in the skies. There are those who thought the aurora were torches held by spirits to light the way to heaven. Finnish and Estonian legends say a whale's tail has slapped the ocean and the spray rose to color the heavens. The Hebrideans thought the red stones of their islands were that color from the blood of heavenly battles, thus the name bloodstone.
One biblical description of the aurora occurs in Maccabees II, 5, 1-4, written about 200 B.C.
About this time Antiochus sent his second expedition into Egypt.
It then happened that all over the city, for nearly forty days, there appeared horsemen charging in midair, clad in garments interwoven with gold—companies fully armed with lances and drawn swords; squadrons of cavalry in battle array, charges and counter charges on this side and that, with brandished shields and bristling spears, flights of arrows and flashes of gold ornaments, together with armor of every sort. Therefore all prayed that this vision might be a good omen.
Aristotle spewed forth some erroneous "astronomy" that had an impact on our ignorance for almost two millennia. One hundred years earlier, a Greek named Anaxagoras had postulated that the aurora, lightening, and comets all came from the earth being bathed in fiery vapors. Keep that in mind for Anaxagoras was far closer to the truth we now know that anyone between then and about 1950. Aristotle criticized him, saying that an interactive relationship between earth and the heavens was absurd. Further, he argued, the heavens were perfect and unchanging.
Galileo (1564-1642) first used the term boreale aurora to describe the northern
lights. Captain James Cook first saw and documented the southern lights on his journey to Antarctica from 1772 to 1775 and named them Aurora Australis.
Mid-eighteenth century scientists explored possibilities that Aristotle was wrong. Hiorter studied the movement of a magnetic needle for 6,638 hours—now that's inductive science—and noticed a correlation with the northern lights. In 1768, Wilcke noted the lights and magnetism aligned similarly. A Frenchman with the delightful name of Jean Jacques d'Ortous de Mairan published the first book on the aurora in 1733. Like Anaxagoras, he looked to the sun for the answer and was ridiculed by others of his time. Humboldt is another man who used inductive science to great advantage. Around 1805, he and an assistant observed a magnetic needle every half hour for thirteen months! Like Hiorter, Humboldt also observed the aurora at times of magnetic disturbance. The Russians further enhanced the use of inductive research by setting up similar observation stations from St. Petersburg to Pekin (Beijing).
Later, Humboldt said "Observations are not really interesting except when we can dispose their results in such a manner as to lead to general ideas." I agree but without those lovely thousands of hours of observation, we would have no foundation for the general idea.
American George Kennan, charged at 23 with laying the telegraph cable across the Bering Strait and Siberia, led an expedition that intrigues me. Kennan's auroral description in Tent Life in Siberia is perhaps the best in literature or science.
The rapid alternations of crimson, blue, green, and yellow in the sky were reflected so vividly from the white surface of the snow, that the whole world seemed now steeped in blood, and then quivering in an atmosphere of pale, ghastly green, through which shone the unspeakable glories of the mighty crimson and yellow arches. But the end was not yet.
Delving into the science of the aurora, we know it is a giant electrical charge that occurs 50 to 70 miles above the earth and sometimes as high as 240 miles. This means to "drive" to the bottom of them would take an hour, and to the top an additional three hours. They are above the ozone layer, above the average height of meteor tracks and are 8 to 20 times farther away from sea level than the top of Mt. Everest and the bottom of cumulonimbus clouds.
Research from the University of Moscow in 1963 first told of the auroral oval that hovers over the north and south poles, and the earth circles between these auroras. Studies at the University of Alaska and Los Alamos as recently as 1967 informed us the northern and southern lights are mirror images of one another.
How does this light happen? Where does this energy come from? Born of the sun, it is always present, at least to polar bears or penguins. Because the rotation of the sun is 27 Earth days beyond 30 degrees latitude, the auroras borealis and australis have a 27-day cycle. Sun spots, and the solar flares which they cause, occur on their largest scales in 11-year cycles. Thus, one season of fall, winter, and spring every 11 years, we see the most profound auroral displays. A great mass of red, the blood red aurora, indicates an intense sun spot. While it takes the light of the sun only eight minutes to come to Earth, it takes the sun spot's visual image two days to journey to our auroral atmosphere. Atmospheric gasses and the magnetic field by the poles cause the presence of the aurora. Molecules and atoms bounce off atmospheric interference, thus creating auroral light. It is these molecular and atomic collisions which cause the colors—nitrogen produces the reds and blues, oxygen the reds and greens.
All of us, at some point in our education, have seen or done a simple scientific experiment with a straight magnet, iron filings, and a piece of paper. Set a magnet on a flat surface and lie a sheet of paper on top. Gently sprinkle the iron filings on it. They will lay in curved lines on the paper on the sides from one end of the magnet to the other, with more collecting in the arc at the each end. Now let your imagination attach color and movement to these curves et voilá, you have an image of the auroras.
The aurora is analogous to and frequently explained by comparison to the neon tube. Indeed, we can consider a neon sign a contained and therefore a captured aurora. The tube in a neon light is filled with a gas that glows when a high voltage runs between the positive electron at one end and the negative electron at the other. The color of the light depends on the gas. The aurora glows different colors when the gas in the atmosphere varies. Atoms and molecules are these gasses and when they touch our atmosphere, an electron hits one of these atoms or molecules. This combination gives off a burst of light. The gasses provide the colors, and the electricity of the magnetic field gives the movement of the lights. Picture a huge, intensely lit, multi-colored round neon tube above one of the poles at an altitude of 50 miles. We see the light and movement that emanates from it.
If that does not work for you, picture water in a stream coming toward, then going around, a rock. The water is trapped by the eddy and rushes around the sides of the rock. Now picture the stream of auroral electromagnetic energy as it comes from the sun toward the Earth. Instead of a water eddy, this solar wind brings electrical energy which becomes trapped by the giant eddy sun-side of the Earth. The rest of the electrical energy rushes past the poles, like the water rushes past the sides of the rock, creating the most intense parts of the aurora.
The most spectacular part of the aurora is the breakup, for it is then the colors change and move the most as the electrical energy dissipates. This breakup causes a flow of colors and light in discrete arcs and bands, or sometimes patches and rays. A corona emanates from the zenith and a veil covers the sky in a glow of one color, most commonly white and, perhaps once in a person's lifetime, red. Other times the aurora moves rapidly with rhythmical change similar to a breeze-blown, undulating ribbon. The auroral pulsation often moves fields of colors with no periods of darkness separating the dancing display.
My mother taught me to watch the northern lights. Perhaps they are the spirits of the dead in ethereal clothes of color, like my mother's silk chiffon, tea-length dress from Paris ... a dark blue georgette hand-painted in rust and gold. The gossamer dress has a dark blue silk under-slip and a 1920s long, flowing, banded headscarf, also of dark blue georgette silk with the hand-painting, that flows past the fingertips. It is a most stunning creation which I'm sure she bought impulsively. I don't know if she ever wore it, but it lay in tissue in the bottom drawer of the Alden family bureau, my bureau in my bedroom, in the company of her cream silk crêpe blouse she wore the day she married my father. The flow of these delicate gossamer silk materials still creates for me the wavy images of the aurora borealis.
In the early 1950s, there was a winter of fantastic displays. We lived in Maine and each winter night when the sky danced, my mother woke me and we stood leaning our arms at almost shoulder height against the cabinets, staring out the north windows at the performance. These windows were about four feet high and extended the full length of the hall and stairway, perhaps 20 feet. It was an odd set of apartments. Where most buildings have the height of the pitch in the center, these had a deep depression and the roofs seemed wings that flared into the northern sky. All the better to see the aurora borealis for there was no roof overhang above. In the black sky we saw pulsating bands vibrating this way and that, the wavy bands of ribbon candy in yellow, white, green, red, blue-violet. One night she woke me and we watched a diffuse white one. It filled the sky and waved back and forth. After watching it for about 20 minutes, she announced, "Oh, this is boring. Let's go back to bed."
We had become inured to brilliant colors that moved, and did not wish to waste our time on white. We watched discrete bands, arcs, folds, draperies, ribbon candy in all sorts of colors, candle flames of color shot through with a breeze as if from an open window. It was during this time that one night we saw an all red aurora—that once in a lifetime occurrence. If I saw it now, I'd weep. Another night, red and green flames of color shot through the midnight like an open fire. They came down, took our souls, tied them together. Beauty was one thing my mother enjoyed immensely.
One day, a couple of years ago, when I was at the beach with the treeless, unlimited sky, I saw another red aurora. I knew how honored I was to see two in my lifetime.
I like the remark Robert Peary made in 1910: "It always is a pity to destroy a pleasant popular illusion: but I have seen auroras of a greater beauty in Maine than I have ever seen beyond the Arctic Circle."
I saw a discrete aurora at West Fork of the Dennison on a Yukon-Alaska trip. One curved band of very pale green inched over the hill out of the north into a question mark without its dot. Six more green question tops gradually followed. As they moved from the north to fill the sky, these questions curved to crescents that hung from zenith to southern horizon. Finally they became nine auroral curtains that rested briefly in the sky at West Fork just over the Canadian border, Alaska side.
I saw the black aurora my first winter here. At first I wondered if it were the negative after-image of the white light. What it is, however, is an absence of aurora in an otherwise sky-filled, pale and subtle, white auroral veil. Neil Davis, auroral scientist at University of Alaska at Fairbanks, says it is an excessive positive charge in the midst of the negative electricity of the northern lights.
I've seen the corona, that crown of light that emanates from the zenith to envelop all my world. I've seen the whole sky ablaze, hardly knowing where to turn to look next. One night, in September 1998, I watched colors that were Crayola Crayon intense as well as pale. What made that September evening unique for me in Alaska was the intensity of color and the aurora filling the entire sky. North shot brilliant-edged thin ribbons in curved, sudden waves of red, violet, orange, pink, yellow, green from the zenith to the northern horizon in seconds. Simultaneously, the South waved gentle whites and pastels, glowed so brilliantly in pale yellow I expected to see the sun rise at 8:30 in the evening, due south.
One night, I saw a round auroral display. Red circles, white circles. Then, a blue one appeared. Too patriotic, I thought. I must be hallucinating. Another blue one. A white one disappeared, then a red one, always round, never an ellipse or an oval.
I think it is the auroras and ice skating that indelibly tie me to the north. I like to skate the white earth, fasten my dreams and skate on ribbon candy, fly in and out among the colored draperies of my mother's silk dress. Some night when it is cold and the ice is clear, I shall leave my warm bed and go skate under the aurora. Some clear winter night, I shall skate the post office pond as the aurora dances.
Sources:
Akasofu, S.-I. Aurora Borealis. Anchorage, Alaska: The Alaska Geographic Society, 1979.
Brown, Neal, Hallinan, Thomas, & Osborne, Daniel. The Aurora Explained. Fairbanks, Alaska: Geophysical Institute of Alaska Fairbanks, 1992. (Video)
Davis, Neil. The Aurora Watcher's Handbook. Fairbanks, Alaska: University of Alaska Press, 1992.
Kennan, George. Tent Life in Siberia. Salt Lake City, Utah: Gibbs-Smith Publishing, 1986. (Originally published, 1871.)
Robert E. Peary. The North Pole, London: Hodder and Stoughton, 1910. (p.172.)
Savage, Candace. Aurora, The Mysterious Northern Lights. Vancouver, BC: Douglas & McIntyre Ltd.
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