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What Time do you Turn the Lights On?The Aurora Borealis
Throughout the ages, there have been countless explanations given for the existence of the Northern Lights ranging from oral legend to scientific theory. One Inuit legend states that the Lights provide evidence of life beyond death. It is believed that the Lights come from spirits carrying torches to guide nomadic travelers on their final journeys. Hopeful gold rush era prospectors believed that the lights were reflections of light shining on the Mother Lode of gold. Today, the most widely accepted scientific explanation is that protons strike gas particles in the earth’s upper atmosphere and produce the dazzling light displays. Solar storms send the protons hurtling across space until their collision with the atmosphere, about 68 miles above the earth.
Although man has known for centuries that the Northern Lights are beautiful and mysterious, recent scientific discoveries have prompted a heightened interest in the fascinating colors and dances of the Northern Lights. These celestial pyrotechnic displays have triggered an influx of winter visitors to Fairbanks. Several area lodges, resorts and tour companies offer Northern Lights tour opportunities. Visitors can view the Northern Lights from a heated “aurorium” cabin, on an overnight dog sled excursion, by a snow cat tour up a mountain, on a horse drawn sleigh ride, or by experiencing one of the many tours to the Arctic Circle. FACTS ABOUT THE AURORA
Aurora has a curtain-like shape, and the altitude of its lower edge is sixty to seventy miles. Like a neon sign, Auroral light is produced by a high-vacuum electrical discharge. It is powered by interactions between the sun and the earth. The light is produced from the glow of the atoms and molecules in the earth’s upper atmosphere. The sun is a ball of gases that is so hot its outermost part blows away as the solar wind. Consisting of charged particles, this tenuous gas travels to earth in about three days. Because the earth’s magnetic field prevents the solar wind from penetrating our atmosphere, its solar particles stream around our planet, encasing earth and its magnetic field within a comet-shaped cavity called the magnetosphere. The solar wind powers the gigantic electrical discharge process, causing the magnetosphere to behave as a generator that produces up to ten million megawatts of electrical power. The upper atmosphere contains, at the lower edge of the aurora, a thin and partly ionized layer called the ionosphere. Reflected by the ionosphere, radio waves can propagate great distances by bouncing between it and the ground. Auroral displays indicate that the ionosphere is energized by the electric power generated in the magnetosphere. As these electrical currents are discharged in the ionosphere, many phenomena are produced, including the visible emissions we recognize as the aurora and magnetic storms. Auroras are similar to color television images. In the picture tube, a beam of electrons controlled by electric and magnetic fields strikes the screen, making it glow in colors that vary with the screen’s phosphor. Auroral color depends on the type of atoms and molecules struck by the energetic particles, particularly electrons, which rain down along earth’s magnetic field lines in the discharge process. Each atmospheric gas glows with a specific color, depending on whether it is ionized or neutral, and on the energy of the particle hitting the atoms and air molecules. The brightest and most common auroral color, a brilliant yellow-green, is produced by oxygen atoms at roughly sixty miles altitude. High altitude oxygen atoms (about 200 miles) produce rare red auroras. Ionized nitrogen molecules produce blue light; neutral nitrogen molecules create purples with red lower borders and ripple edges. Auroral intensity varies from night to night. During a single night, the best viewing is usually from late evening through the early morning hours. Strong auroras can be seen in the continental U.S., particularly in the north, during sunspot maximum years. The number of sunspots (sign of solar activity) varies according to an eleven-year cycle. A few years after a maximum sunspot year, auroras in high latitude are more numerous. More auroras can usually be seen in the spring and the fall. The magnetosphere protects us from direct effects of the solar wind, but Auroras can seriously disrupt radio communications, radio navigation, some defense-related radar systems, and power transmission lines. Currents created by changing magnetic fields accompanying Aurora causes corrosion in pipes, including the Alaska Pipeline. Information about the Aurora Produced by Edited by Dave Shultz |
TM
The
Aurora Borealis or Northern Lights, one of Fairbanks’ most popular visitor
attractions, has been a natural phenomenon in the northern sky since the
beginning of time. Dr. Syun-Ichi Akasofu, Director of the International
Arctic Research Center, describes the Northern Lights as “gigantic neon
signs with high volume electrical discharge.” These flashing “neon signs”
are luring large numbers of visitors to Fairbanks from all over the world.
The
lights created extend for hundreds of miles into space. The colors range
from green to red to purple. The brightest and most common color is a
yellow-green. Because of Fairbanks’ location, it is one of the best places
on earth to see the Northern Lights. Researchers have discovered that
auroral displays ebb and increase on an eleven year cycle. The peak of the
most recent cycle was the winter of 1992.
Auroras
occur along ring-shaped regions around the north and south geomagnetic
poles. At the South Pole the lights are called Aurora Australis and at the
North Pole they are known as the Northern Lights or the Aurora Borealis.
Because of the geographic location of Fairbanks, the Lights can easily be
seen here.