Australia's southern skies light-up with Southern Lights or Aurora Australis | Daily Mail Online Next Forget the Northern Lights... here's the Southern Spectacular: Australia's skies are lit up with the fantastic colours of the Aurora Australis The Aurora Australis or 'Southern Lights' is best seen in parts of Tasmania on a clear and cold night's sky It is the Southern Hemisphere's version of the Aurora Borealis or 'Northern Lights' best seen in North America The phenomenon occurs when electrons emanating from the sun and gases in the upper atmosphere collide The result is this illuminating spectrum of green, purple, yellow and red lights streaking across the sky What causes the northern lights? | Earth | EarthSky What causes the northern lights? By Eleanor Imster in Earth | January 8, 2016 They are an ethereal display of colored lights shimmering across the night sky – the aurora borealis or northern lights. What causes them? Photo by Ruslan Merzlyakov. Visit him on Facebook. Those who live at or visit high latitudes might at times experience colored lights shimmering across the night sky. Some Inuit believed that the spirits of their ancestors could be seen dancing in the flickering aurora.

In Norse mythology, the aurora was a fire bridge to the sky built by the gods. This ethereal display – the aurora borealis or aurora australis, the northern or southern lights – is beautiful. What causes these lights to appear? Our sun is 93 million miles away. But its effects extend far beyond its visible surface. Great storms on the sun send gusts of charged solar particles hurtling across space. If Earth is in the path of the particle stream, our planet’s magnetic field and atmosphere react. When the charged particles from the sun strike atoms and molecules in Earth’s atmosphere, they excite those atoms, causing them to light up. What does it mean for an atom to be excited? Atoms consist of a central nucleus and a surrounding cloud of electrons encircling the nucleus in an orbit. When charged particles from the sun strike atoms in Earth’s atmosphere, electrons move to higher-energy orbits, further away from the nucleus. Then when an electron moves back to a lower-energy orbit, it releases a particle of light or photon. What happens in an aurora is similar to what happens in the neon lights we see on many business signs.

Electricity is used to excite the atoms in the neon gas within the glass tubes of a neon sign. That’s why these signs give off their brilliant colors. The aurora works on the same principle – but at a far more vast scale. When charged particles from the sun strike air molecules in Earth's magnetic field, they cause those molecules' atoms to become excited. The molecules give off light as they calm down. Image Credit: NASA The aurora often appears as curtains of lights, but they can also be arcs or spirals, often following lines of force in Earth’s magnetic field. Most are green in color but sometimes you’ll see a hint of pink, and strong displays might also have red, violet and white colors. The lights typically are seen in the far north – the nations bordering the Arctic Ocean – Canada and Alaska, Scandinavian countries, Iceland, Greenland and Russia. But strong displays of the lights can extend down into more southerly latitudes in the United States. And of course, the lights have a counterpart at Earth’s south polar regions. The colors in the aurora were also a source of mystery throughout human history. But science says that different gases in Earth’s atmosphere give off different colors when they are excited.

Oxygen gives off the green color of the aurora, for example. Nitrogen causes blue or red colors. So today the mystery of the aurora is not so mysterious as it used to be. Yet people still travel thousands of miles to see the brilliant natural light shows in Earth’s atmosphere. And even though we know the scientific reason for the aurora, the dazzling natural light show can still fire our imaginations to visualize fire bridges, gods or dancing ghosts. Jennifer Khordi captured this aurora on September 7, 2015 over the Catskills of New York state. Visit Jennifer Khordi on Facebook. Aurora just west of Saskatoon, by Colin Chatfield. He said, “We were just about to leave as the Aurora was just a dull band, then it came alive for about an hour or so. This was taken at 2:02am on January 27, 201] … It is not very visible, but I caught Comet Lovejoy at centre left of this photo.” “This photo was captured a couple of hours ago in Nordreisa, Norway.

I was dressed in my very best winter clothes and I can easily admit that I was freezing most of the time anyways, 22 below (-7.6 fahrenheit) kinda has that effect.” January, 2015. © 2015 Tor-Ivar Næss Aurora in Vesterlålen, Norway by Stig Hansen Mike Taylor in Maine caught this photo in September, 2014. More about Mike and this photo. Photo © Tor-Ivar Næss Aurora borealis over Norway’s Steinvikholmen Castle by Hallvor Hobbyfotograf Lillebo. View larger. | Photo credit: Hallvor Hobbyfotograf Lillebo Reisafjorden, Norway bathing in auroras on January 2, 2014. When charged particles from the sun strike atoms in Earth’s atmosphere, they cause electrons in the atoms to move to a higher-energy state. When the electrons drop back to a lower energy state, they release a photon: light. This process creates the beautiful aurora, or northern lights. Image copyright 2014 Tor-Ivar Næss. Via WaitForIt on Facebook. View larger. | Mike Taylor calls this photo Moonlight Aurora II.

He captured it on February 19, 2014. Visit Taylor Photography View larger. | Aurora over Mt. Hood in Oregon as captured by Ben Coffman Photography during the night of May 31-June 1, 2013. Visit Ben’s photography page on G+ or visit Ben on Facebook . Aurora on January 1, 2014 by Geir-Inge Bushmann. The lights typically are seen in the far north – the nations bordering the Arctic Ocean – Canada and Alaska, Scandinavian countries, Iceland, Greenland and Russia. See more photos from Geir-Inge Bushmann View larger. | Aurora seen by EarthSky Facebook friend Colin Chatfield in Saskatchewan, Canada on May 19, 2012. View larger. | Spectacular aurora, or northern lights, seen by EarthSky Facebook friend Colin Chatfield in Saskatchewan, Canada on October 24, 2011. Bottom line: When charged particles from the sun strike atoms in Earth’s atmosphere, they cause electrons in the atoms to move to a higher-energy state. When the electrons drop back to a lower energy state, they release a photon: light.

This process creates the beautiful aurora, or northern lights. What are the northern lights?(Everyday Mysteries: Fun Science Facts from the Library of Congress) What are the northern lights? The northern lights, one of several astronomical phenomena called polar lights (aurora polaris), are shafts or curtains of colored light visible on occasion in the night sky. Polar lights (aurora polaris) are a natural phenomenon found in both the northern and southern hemispheres that can be truly awe inspiring. Northern lights are also called by their scientific name, aurora borealis, and southern lights are called aurora australis. Sten Odenwald, author of The 23rd cycle, learning to live with a stormy star (New York, Columbia University Press, c2001), provides insight to how northern lights are formed: The origin of the aurora begins on the surface of the sun when solar activity ejects a cloud of gas. Scientists call this a coronal mass ejection (CME). If one of these reaches earth, taking about 2 to 3 days, it collides with the Earth’s magnetic field.

This field is invisible, and if you could see its shape, it would make Earth look like a comet with a long magnetic ‘tail’ stretching a million miles behind Earth in the opposite direction of the sun. When a coronal mass ejection collides with the magnetic field, it causes complex changes to happen to the magnetic tail region. These changes generate currents of charged particles, which then flow along lines of magnetic force into the Polar Regions. These particles are boosted in energy in Earth’s upper atmosphere, and when they collide with oxygen and nitrogen atoms, they produce dazzling auroral light. Odenwald further tells us "Aurora are beautiful, but the invisible flows of particles and magnetism that go on at the same time can damage our electrical power grid and satellites operating in space. This is why scientists are so keen to understand the physics of aurora and solar storms, so we can predict when our technologies may be affected." Can I see them anywhere? Yes. Although more frequent at higher latitudes, closer to the poles (such as in Canada, Alaska, Antarctica), they have been seen closer to the equator as far south as Mexico.

To view them, look in the direction of the closest pole (the northern horizon in the northern hemisphere, the southern horizon in the southern hemisphere). Can I see them at any time of the year? Yes. In some areas, such as Alaska or Greenland, they may be visible most nights of the year. And they occur at any time of the day, but we can’t see them with the naked eye unless it’s dark. What causes the colors and patterns? Colors and patterns are from the types of ions or atoms being energized as they collide with the atmosphere and are affected by lines of magnetic force. Displays may take many forms, including rippling curtains, pulsating globs, traveling pulses, or steady glows. Altitude affects the colors. Blue violet/reds occur below 60 miles (100 km), with bright green strongest between 60-150 miles (100-240 km). Above 150 miles (240 km) ruby reds appear.

Fun Facts about northern lights: According to Neil Bone (The aurora: sun-earth interactions, 1996), the term aurora borealis--northern dawn--is jointly credited to have first been used by Pierre Gassendi (1592-1655) and Galileo Galilei (1564-1642), who both witnessed a light display on Sept. 12, 1621. However, Bone also includes a description of the northern lights made 1,000 years prior by Gregory of Tours (538-594.) It included the phrase, "... so bright that you might have thought that day was about to dawn." Auroras have been observed since ancient times. The height of the displays can occur up to 1000 km (620 miles), although most are between 80-120 km. Auroras tend to be more frequent and spectacular during high solar sunspot activity, which cycles over approximately eleven years. Some displays are particularly spectacular and widespread and have been highlighted in news accounts.

Examples include auroral storms of August-September, 1859, Feb 11, 1958, (lights 1250 miles wide circled the Arctic from Oregon to New Hampshire) and March 13, 1989, (the whole sky turned a vivid red and the aurora was seen in Europe and North America as far south as Cuba). Legends abound in northern cultures to explain the northern lights. Some North American Inuit call the aurora aqsarniit (“football players”) and say the spirits of the dead are playing football with the head of a walrus. Often legends warn children that the lights might come down and snatch them away. June 1896, Norwegian Kristian Birkeland, the “father of modern auroral science,” suggested the theory that electrons from sunspots triggered auroras. Yellowknife (Northwest Territories, Canada) is the capital for aurora tourism. The earliest known account of northern lights appears to be from a Babylonian clay tablet from observations made by the official astronomers of King Nebuchadnezzar II, 568/567 BC.

Some people claim to hear noises associated with the northern lights, but documenting this phenomenon has been difficult. Related Web Sites Aurora borealis by Pål Brekke - This is an article on the aurora borealis by Pål Brekke published in Scandinavian Review, Fall 2008, v. 93. Auroras: Paintings in the Sky - Lots of links, pictures, includes specific information for teachers. Cosmicopia: an abundance of cosmic rays - Information on Space Weather from NASA, including an animation of a coronal mass ejection's impact on the Earth's magnetosphere. NOAA POES Auroral Activity - Technical information and data collected from POES (Polar-orbiting Operational Environmental Satellite) on its most recent polar pass. May help predict where to see auroras. Solar Storms - This site presents information about the human impacts of solar storms and space weather. Space Weather Research Explorer: Auroras - With data from POES, this Exploratorium site packages the information in a simpler format. Further Reading Aurora - YouTube Aurora Want to watch this again later? Sign in to add this video to a playlist. Need to report the video? Sign in to report inappropriate content. Rating is available when the video has been rented.

This feature is not available right now. Please try again later. Uploaded on Jun 10, 2007 New Antarctica Feature Film: Go to for a higher resolution version of this clip. Time-lapse footage of the Aurora Australis, or Southern Lights. This is the Southern Hemisphere equivalent of the Aurora Borealis or Northern Lights. Filmed during the Antarctic winter in the general vicinity of McMurdo Station and Scott Base, where the sun is below the horizon for 4 months of the year. Most of the individual clips here were each taken over about a 10 minute period to give you an idea of how much they were moving in real time. Have a look at my time-lapse clip "A Year on Ice" for more Antarctic footage which includes other aurora clips in the winter section. The specific music used is by Danny Elfman from the Black Beauty soundtrack, the track is called "Memories"... available at most music retailers.

Aurora Borealis: What Causes the Northern Lights & Where to See Them Aurora Borealis: What Causes the Northern Lights & Where to See Them By SPACE.com Staff | February 10, 2015 08:15pm ET MORE Skywatcher Shawn Malone took this photo of the aurora March 15-16, 2012. She writes: "[A]urora activity picking up casts a bright reflection off of Lake Superior, Marquette, MI." Credit: Shawn Malone The northern lights, or aurora borealis, offer an entrancing, dramatic, magical display that fascinates all who see it — but just what causes this dazzling natural phenomenon? At the center of our solar system lies the sun, the yellow star that sustains life on our planet. The sun's many magnetic fields distort and twist as our parent star rotates on its axis. When these fields become knotted together, they burst and create so-called sunspots . Usually, these sunspots occur in pairs; the largest can be several times the size of Earth's diameter.

This image from NASA's Solar Dynamics Observatory shows the sun as it appeared in extreme ultraviolet wavelengths on March 5, 2012 just after a major solar flare. Credit: NASA/SDO/AIA At the center of the sun, the temperature is 27 million degrees Fahrenheit (15 million degrees Celsius). As the temperature on its surface rises and falls, the sun boils and bubbles. Particles escape from the star from the sunspot regions on the surface, hurtling particles of plasma, known as solar wind, into space. It takes these winds around 40 hours to reach Earth. When they do, they can cause the dramatic displays known as the aurora borealis. [Infographics: How the Northern Lights Work & Anatomy of Sun Storms & Solar Flares ] Sunspots and cycles The sunspots and solar storms that cause the most magnificent displays of the northern lights occur roughly every 11 years. The solar cycle peaked in 2013, but it was the weakest solar maximum in a century. [ Photos: Amazing Auroras of 2014 ] "This solar cycle continues to rank among the weakest on record," Ron Turner of Analytic Services, Inc.

who serves as a Senior Science Advisor to NASA's Innovative Advanced Concepts program, said in a statement. Since record-keeping of the ebb and flow of the sun's activity began in 1749, there have been 22 full cycles. Researchers monitor space weather events because they have the potential to affect spacecraft in orbit, knock out power grids and communications infrastructure on Earth, and amp up normal displays of the northern and southern lights. Scientists are also investigating how fluctuations in the sun's activity affect weather on our planet. Particles and polar attraction Earth is constantly bombarded with debris, radiation and other magnetic waves from space that could threaten the future of life as we know it. Most of the time, the planet's own magnetic field does an excellent job of deflecting these potentially harmful rays and particles, including those from the sun. Particles discharged from the sun travel 93 million miles (around 150 million km) toward Earth before they are drawn irresistibly toward the magnetic north and south poles. As the particles pass through the Earth's magnetic shield , they mingle with atoms and molecules of oxygen, nitrogen and other elements that result in the dazzling display of lights in the sky.

An Expedition 30 crew member took this photo of the North Atlantic with an aurora on March 28, 2012. Credit: NASA The auroras in Earth's Northern Hemisphere are called the aurora borealis. Their southern counterpart, which light up the Antarctic skies in the Southern Hemisphere, are known as the aurora australis . What causes the colors? The colors most often associated with the aurora borealis are pink, green, yellow, blue, violet, and occasionally orange and white. Typically, when the particles collide with oxygen, yellow and green are produced. Interactions with nitrogen produce red, violet, and occasionally blue colors. The type of collision also makes a difference to the colors that appear in the sky: atomic nitrogen causes blue displays, while molecular nitrogen results in purple. The colors are also affected by altitude. The green lights typically in areas appear up to 150 miles (241 km) high, red above 150 miles; blue usually appears at up to 60 miles (96.5 km); and purple and violet above 60 miles.

These lights may manifest as a static band of light, or, when the solar flares are particularly strong, as a dancing curtain of ever-changing color. History of the auroral lights For millennia, the lights have been the source of speculation, superstition and awe. Cave paintings in France thought to date back 30,000 years have illustrations of the natural phenomenon. In more superstitious times, the northern lights were thought to be a harbinger of war or destruction, before people really understood what causes them. Many classic philosophers, authors and astronomers, including Aristotle, Descartes, Goethe and Halley, refer to the northern lights in their work. As early as 1616, the astronomer Galileo Galilei used the name aurora borealis to describe them, taking the name of the mythical Roman goddess of the dawn, Aurora, and the Greek name for wind of the north, Boreas. The aurora australis, or the southern lights, occur around the south polar region. But, since the South Pole is even more inhospitable than the North Pole, it is often trickier to view the southern lights.

Astrophotographer Antti Pietikäinen took this aurora photo on Jan. 24, 2012 in Muonio, Lapland, Finland. Credit: Antti Pietikainen Where to see the lights The best places to see the northern lights are Alaska and northern Canada, but visiting these vast, open expanses is not always easy. Norway, Sweden and Finland also offer excellent vantage points. During periods of particularly active solar flares, the lights can be seen as far south as the top of Scotland and even northern England. [ A Guide for Watching Earth's Auroras ] On rare occasions, the lights are seen farther south. They were first observed by European settlers in New England in 1791. In "Historical Storms of New England," published in 1891, Sidney Perley wrote, "May 15, 1719, the more beautiful and brilliant aurora borealis was first observed here as far as any record or tradition of that period inform us, and it is said that in England it was first noticed only three years before this date.

In December of the same year the aurora again appeared, and the people became greatly alarmed, not dreading it so much as a means of destruction but as precursor of the fires of the last great day and a sign of coming dangers." When to see the lights The northern lights are always present, but winter is usually the best time to see them, due to lower levels of light pollution and the clear, crisp air. September, October, March and April are some of the best months to view the aurora borealis. The lights are known to be brighter and more active for up to two days after sunspot activity is at its highest. Several agencies, such as NASA and the National Oceanic and Atmospheric Administration , also monitor solar activity and issue aurora alerts when they are expected to put on a particularly impressive show. Additional reporting by Nola Taylor Redd, Space.com Contributor Additional resources Northern Lights or Aurora Borealis Explained What are Northern Lights? The bright dancing lights of the aurora are actually collisions between electrically charged particles from the sun that enter the earth's atmosphere. The lights are seen above the magnetic poles of the northern and southern hemispheres.

They are known as 'Aurora borealis' in the north and 'Aurora australis' in the south.. Auroral displays appear in many colours although pale green and pink are the most common. Shades of red, yellow, green, blue, and violet have been reported. The lights appear in many forms from patches or scattered clouds of light to streamers, arcs, rippling curtains or shooting rays that light up the sky with an eerie glow. What causes the Northern Lights? The Northern Lights are actually the result of collisions between gaseous particles in the Earth's atmosphere with charged particles released from the sun's atmosphere. Variations in colour are due to the type of gas particles that are colliding. The most common auroral color, a pale yellowish-green, is produced by oxygen molecules located about 60 miles above the earth. Rare, all-red auroras are produced by high-altitude oxygen, at heights of up to 200 miles. Nitrogen produces blue or purplish-red aurora. The connection between the Northern Lights and sunspot activity has been suspected since about 1880.

Thanks to research conducted since the 1950's, we now know that electrons and protons from the sun are blown towards the earth on the 'solar wind'. (Note: 1957-58 was International Geophysical Year and the atmosphere was studied extensively with balloons, radar, rockets and satellites. Rocket research is still conducted by scientists at Poker Flats, a facility under the direction of the University of Alaska at Fairbanks - see web page The temperature above the surface of the sun is millions of degrees Celsius. At this temperature, collisions between gas molecules are frequent and explosive. Free electrons and protons are thrown from the sun's atmosphere by the rotation of the sun and escape through holes in the magnetic field. Blown towards the earth by the solar wind, the charged particles are largely deflected by the earth's magnetic field. However, the earth's magnetic field is weaker at either pole and therefore some particles enter the earth's atmosphere and collide with gas particles. These collisions emit light that we perceive as the dancing lights of the north (and the south).

The lights of the Aurora generally extend from 80 kilometres (50 miles) to as high as 640 kilometres (400 miles) above the earth's surface. Where is the best place to watch the Northern Lights? Northern Lights can be seen in the northern or southern hemisphere, in an irregularly shaped oval centred over each magnetic pole. The lights are known as 'Aurora borealis' in the north and 'Aurora australis' in the south. Scientists have learned that in most instances northern and southern auroras are mirror-like images that occur at the same time, with similar shapes and colors. Because the phenomena occurs near the magnetic poles, northern lights have been seen as far south as New Orleans in the western hemisphere, while similar locations in the east never experience the mysterious lights. However the best places to watch the lights (in North America) are in the northwestern parts of Canada, particularly the Yukon, Nunavut, Northwest Territories and Alaska. Auroral displays can also be seen over the southern tip of Greenland and Iceland, the northern coast of Norway and over the coastal waters north of Siberia.

Southern auroras are not often seen as they are concentrated in a ring around Antarctica and the southern Indian Ocean. Areas that are not subject to 'light pollution' are the best places to watch for the lights. Areas in the north, in smaller communities, tend to be best. When is the best time to watch for auroral displays? Researchers have also discovered that auroral activity is cyclic, peaking roughly every 11 years. The next peak period is 2013. Winter in the north is generally a good season to view lights. The long periods of darkness and the frequency of clear nights provide many good opportunities to watch the auroral displays. Usually the best time of night (on clear nights) to watch for auroral displays is local midnight (adjust for differences caused by daylight savings time). Legends of the Lights 'Aurora borealis', the lights of the northern hemisphere, means 'dawn of the north'. 'Aurora australis' means 'dawn of the south'. In Roman myths, Aurora was the goddess of the dawn. \par Many cultural groups have legends about the lights. In medieval times, the occurrences of auroral displays were seen as harbingers of war or famine.

The Maori of New Zealand shared a belief with many northern people of Europe and North America that the lights were reflections from torches or campfires. The Menominee Indians of Wisconsin believed that the lights indicated the location of manabai'wok (giants) who were the spirits of great hunters and fishermen. The Inuit of Alaska believed that the lights were the spirits of the animals they hunted: the seals, salmon, deer and beluga whales. Other aboriginal peoples believed that the lights were the spirits of their people. Northern and Southern Lights Home Sun & Moon Northern Lights What Are Northern and Southern Lights? An aurora is a natural electric phenomenon that creates bright and colorful light displays in the sky. They are common at higher latitudes, mostly within the Arctic and the Antarctic Circles. Aurora borealis as seen in Michigan, U.S.A. The northern lights can be green, pink, red, blue or violet in color. ©iStockphoto.com/Constance McGuire In the Arctic Circle, they are known as aurora borealis or the northern lights, while in the Antarctic Circle they are called aurora australis or the southern lights.

These dramatic and colorful lights are created when electrically charged particles from solar winds enter the Earth’s atmosphere and interact with gases in the atmosphere. Stream of High Energy Particles The Sun continuously emits electromagnetic radiation and highly energized particles into space, which produce space weather. Solar wind is part of space weather. It is a continuous stream of highly energized particles – mostly electrons and protons – that flow out from the Sun through space at very high speeds and high temperature. Solar winds can reach speeds of one million miles per hour. Earth: A Giant Magnet The Earth is a giant magnet, with its magnetic field extending from the Earth’s core to the area in space where it meets solar winds. The region of this field where the Earth’s magnetic influence dominates over solar winds is known as the magnetosphere. Its shape and size continuously change as it gets bombarded by solar winds. The Earth’s magnetosphere shields the Earth from solar winds and other harmful cosmic rays. It deflects most of the highly charged particles from solar winds and stops them from entering the Earth’s atmosphere.

High Energy Collisions While the Earth’s magnetosphere is responsible for protecting it from the highly charged particles in the solar wind, sometimes, when the conditions are right, these particles enter the Earth’s atmosphere at the two poles, where they collide and interact with gas molecules and atoms. When such collisions occur, the energy from the electrons in the solar winds is transferred to electrons in the atoms of different atmospheric gases. Any excess energy is then released by these excited atoms in the form of light. Auroral light displays tend to occur at between 50 miles (80.46 kilometers) and 200 miles (321.87 kilometers) above the surface of the Earth. Many Different Colors The color of the light released depends on the kind of gas molecules, their electrical state at the time of collision, and the type of the solar wind particles they collide with. Oxygen atoms emit yellow-green or red colored light, while nitrogen atoms generate blue or purplish-red colored light. A mix of gases in the Earth’s atmosphere creates multicolored auroras.

Because particles from solar winds continually enter the Earth’s atmosphere and interact with gas atoms, aurora displays can be static as well as dynamic – they can change shape and colors, and pulsate in the skies. And Many Different Shapes Aurora Borealis, Alaska Kids' Corner, State of Alaska From "The Ballad of the Northern Lights" by Robert Service by Dr. Neil Davis (reprint) The Aurora, also known as the Northern Lights, has mystified people down through the ages, scientists, poets, and lay persons alike. Written records of so-called "great auroral displays" date back more than two thousand years. Sometimes the Aurora over Alaska and other auroral zones is barely visible or appears colorless and unmoving. But at other times the auroras can be incredibly bright, multihued and fast moving. Tall green curtains of lights, red tipped at their bottoms, stretch from horizon to horizon. They ripple and sway, fold and unfold, then suddenly disappear, only to reform in a new shape minutes later. For those who live in Alaska, the Aurora is a part of northern life. Fall, winter and spring is the special season for viewing the great lights for residents and off-season visitors.

Some Alaskans have "Aurora Alerts;" when a display begins, the first person to spot them begins a phone tree to get the word out. The "pulsating Aurora" is one form of Northern Light common during the post-midnight hours. It blinks on and off every few seconds as though controlled by some mysterious unseen hand in the sky flicking a switch. The great auroral displays are spectacular global events during which the Aurora spreads down from the polar regions to cover as much as two thirds of the earth's skies with bright, fast-moving masses of light, often deep red in color. The rare "great auroral displays" follow one or two days of violent solar flares in the vicinity of major sunspots. These solar flares cast out vast streams of electrically charged particles which stream down into the earth's atmosphere. These particles, mostly electrons and protons, are steered away from the tropical regions by the earth's magnetic field. Striking the gases of the earth's high atmosphere, the charged particles glow.

It is exactly the same thing that happens in a television tube: complex streams of electrons within the TV strike the phosphor coated face of the tube, and cause it to glow, creating the colored moving patterns we see from our living room couches. Outside, at night, we can look up at that great star-studded television tube in the sky; if the Aurora is out and no clouds are about, the colored patterns will be there too. Even though "great auroral displays" appear infrequently, spectacular displays of Aurora are common in Alaska and other auroral zone locations. This is because the sun is always sending out a stream of electrons and protons. They make up the solar wind which blows constantly toward the earth and other planets. Enough of the solar wind particles come into the earth's high atmosphere at the auroral zone to create continuous Aurora, summer, winter, fall and spring. Although much is known about the Aurora, this fascinating phenomenon still withholds some of its mysteries. For example, scientists do not yet understand why the Aurora is so highly structured. For the University of Alaska Fairbanks, this continues to be an important area of study.

The most beautiful Aurora is composed of thin sheets that stretch upward a hundred miles or more and extend across the sky from horizon to horizon, like gigantic ribbons set on edge high above and parallel to the earth's surface. These arcs and bands whip and weave across the sky, and bright rays ripple along them at fantastic speed. Some of these intricate multicolored forms have a thickness of only 100 meters, about the length of a football field, yet may be several hundred kilometers tall and well over 1,000 kilometers in length. It boggles the mind to realizeas has been proven by simultaneous observation in the two hemispheresthat these sharply defined auroral forms have an identical or nearly identical mate in the southern hemisphere, out of sight and almost a world away. Joined together by an invisible magnetic bond that arches far above the Equator, each pair of mated auroral dancers move across the cold polar skies in perfect harmony. Each motion or brightness change in one hemisphere is mirrored in the other, on a time scale of less than a fraction of a second. A most curious and highly controversial question involves auroral sound. Although I've never heard one, my wife has and so have several scientists I know.

Some reports of hearing noises associated with auroral displays may be erroneous impressions, but I am convinced many others are not. Hundreds of written reports indicate noises are sensed when a particular type of fast-Aurora is nearly overhead. Some people sense whistling and crackling noises, even when they close their eyes. The reports of auroral sound make it certain that the unknown cause of the apparent sound is in the vicinity of the hearer, not in the Aurora itself. Most likely, the reported noises are related to electrical phenomena which accompany certain types of bright Aurora. No matter how many auroras one may have seen, a good high-latitude display, as seen in Alaska, sends tingles up the viewer's spine. Even a moderate display seen at the auroral zone in the 49th state can be far more exciting to watch than one of the rare "great displays." The best of words and photographs fail to capture the magnificence of the high-latitude Aurora, although some of Robert Service's poetry may come close. THE AURORA has a curtain-like shape, and the altitude of its lower edge is sixty or seventy miles, about ten times higher than a jet aircraft flies.

AURORAS OCCUR along ring-shaped regions around the north and south geomagnetic poles. Fairbanks, Alaska, is a good place for Aurora watching because it is under this region in the north, where people see Aurora Borealis, or northern lights; the southern Aurora is Aurora Australis. LIKE A NEON SIGN, auroral light is produced by a high-vacuum electrical discharge. It is powered by interactions between the sun and earth. The light is a glow from 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 and our protective atmosphere are being 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 strike 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, that 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 60 miles altitude. High-altitude oxygen atoms (about 200 miles) produce rare, all-red auroras.

Ionized nitrogen molecules produce blue light, neutral nitrogen molecules create purplish-red lower borders and ripple edges. AURORAL INTENSITY varies from night to night and during a single night, with best viewing 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 (a sign of solar activity) varies according to an eleven-year cycle a few years after a maximum sunspot year (such as 1991), auroras in high-latitude are more numerous. There's also a slight tendency for more auroras in spring and 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. Current created by changing magnetic fields accompanying Aurora cause corrosion in pipes, including the trans-Alaska pipeline. Come to Interior or Northern Alaska during the late fall or winter months, particularly March when the skies are often clear and dark. Plan to spend a few days because the Aurora is, like the weather, variable. Aurora-watching and auroral photography is best done on clear, moonless nights.

When flying between Seattle and Anchorage or Fairbanks in wintertime, take a night flight and sit on the right-hand side of the airplane going north (left-hand side of the airplane going south). Don't be misled by seeing Aurora below the aircraft's wing; that Aurora is high over western Canada, at least 50 miles above the ground. The places where the auroral forms appear to "touch" the ground are about 600 miles distant. To be sure of seeing Aurora, plan to stay up most of the night. The best hours often are near midnight. Wear warm clothing. Stay away from city or other bright lights that can obscure the views. For a real treat, go to a hot springs resort where you can lay in an outdoor hot pool and watch the Aurora in comfort. If you plan to photograph the Aurora, bring a tripod. Bright as it is, the Aurora still requires time exposures of several seconds. Summer visitors to Fairbanks can view and purchase a video tape showing actual auroral motions at the University Museum. Each evening at nearby Ester, Alaska, Photosymphony Productions puts on a unique musical and photographic show entitled "The Crown Of Light" containing some of the finest photographic images of Aurora available anywhere.

Links for More Information: Secrets of the Polar Aurora [an error occurred while processing this directive] (File loads promptly Images take longer) Secrets of the Polar Aurora For a remarkable two-minute video of aurora, click here by David P. Stern From talk presented in Anchorage, Alaska, 11 August 2002 Typical aurora (Dick Hutchinson ©) Alaska is known as a good place for seeing the polar aurora, also known as "Northern Lights." Originally the phenomenon was named "Aurora Borealis," Latin for "northern dawn," since in the lower 48 states or in mid-Europe it may appear (on the rare occasions when it does) as a glow on the northern horizon, as if the sun was rising from the wrong direction. But the southern hemisphere has the same phenomenon, with the glow coming from the south, so scientists prefer to call it simply the "Polar Aurora." Most visitors to Alaska never get to see an aurora, because they come in the summer, when skies are rarely dark enough. Alaskans claim that only around August 16 does the sky get dark enough to see stars, which is when aurora stands out.

After that date, your best bet is to go to Fairbanks--and since the brightest auroras occur around midnight (or later, due to Alaska's time zone), you might have to stay up a long time. Perhaps it is better then to ask the night clerk at your hotel to ring you up if a good display becomes visible. Appearance and relation to magnetism What does it look like? Most often, you see greenish white ribbons stretching across the sky, roughly from east to west, usually with waves in them. In Fairbanks they could be overhead, in northern Norway or Sweden too, sometimes even in Winnipeg. Further south those ribbons tend to be near the northern horizon. And if you look closely at them, you will note that they contain many parallel rays, running across their width (see picture below). Two things about those rays. One, the bright ones fade while dim ones brighten instead--a bit like flames in a fireplace, and just as mesmerizing. Some auroras are deep red, and these may be just a shapeless glow--or they may have rays, too. And second, the direction of those rays is related to the magnetism of the Earth.

The aurora--a woodcut by Fridtjof Nansen Anyone who has ever used a compass knows that the Earth is a giant magnet. The needle of the compass usually points towards one of two points, the magnetic poles of the Earth, located near the geographic poles. But because the compass needle is mounted horizontally, it does not show everything. Actually, the magnetic force points not just northward but also slants down into the Earth. Compass needles carefully balanced on a horizontal axis ("dip needles") point in that slanting direction, when allowed to swing in a north-south vertical plane. In fact, the angle gets steeper the closer one gets to the magnetic pole. At the pole the force is vertical. The rays of the aurora faithfully follow that slanting direction. The Auroral Zone That was one clue that the aurora was related to the Earth's magnetism. The other clue was found by keeping tabs on how often aurora was seen in various locations. It turned out that the important factor was distance from the magnetic pole. That pole is separated from the geographic pole, marking the Earth's rotation axis, and currently it is in the Arctic Ocean, just north of Canadian soil.

The fact it is displaced towards America means Americans do not have to go as far north to see aurora as do, say, residents of Siberia, on the other side of the globe. Locations about 1500 miles from the magnetic pole are where aurora is seen most frequently: further away or nearer to the magnetic pole, they get more rare (they are quite rare at the magnetic pole itself). Fairbanks, Alaska, at the edge of the "auroral zone, " makes a good observation post. What you usually see there are those quiet curtains and ribbons. But not always. At some times they change shape rapidly, advance, retreat or bulge out in a violent fashion, and they also get quite bright. Scientists call such an active, violent outburst an "auroral substorm, " and satellites still study the release of energy, far in space, which causes it. If you are lucky you may also see a "corona"--a burst of rays radiating in all directions. That is a caused by perspective--like the rays of the sun setting behind a cloud--and it means it the rays of the aurora are arriving right overhead. Is the polar aurora rare? Depends on where you are!

If your home is in Fairbanks, or in Tromso, Norway, or Fort Churchill, Canada--not at all. You won't see it every evening, but it is present frequently enough. In Washington D.C., or London, or Beijing, however, it is a rare event, seen only when the Sun creates "stormy conditions." On such occasions--especially near the peak of the 11-year sunspot cycle--the Sun sends out a dense cloud of hot gas, whose arrival disturbs the Earth's magnetic environment and produces a so-called "magnetic storm" (more details, further below). Magnetic storms expand the auroral zone to locations more distant from the magnetic pole--such as Washington, London or Beijing--and also create bright auroras. If this happens on a clear night, residents in those cities can see an aurora, but it is a rare treat for them. On the right is a satellite image of an aurora extending to the "lower 48 states" of the US (note Florida, outlined by its city lights). Later that day, in March 1989, the aurora actually spread much further southward, but no satellite was in position to photograph it then.

The next picture below is of a 2001 aurora seen in Purcellville, Virginia. Electrons of the Aurora To early observers, and well into the 20th century, the polar aurora was a great mystery. Not everything is solved even now--but thanks largely to space satellites, we have a fair understanding of the way the aurora is produced. First question-- how high up is it? By comparing photographs taken from separated locations, an altitude of about 60 miles was found for the green aurora, and up to about twice as much for the red one. Clues like that led scientists to conclude that "something out there" was shooting towards us beams of fast electrons, somewhat like the ones painting the picture inside a TV picture tube. In a TV, electrons hit a screen, come to a stop, and their energy is converted to light. Something similar happens with the electrons that cause the aurora: they collide with atoms in the upper fringes of the atmosphere, give up their energy to those atoms and cause them to emit light. And what are electrons? Tiny particles with negative electric charge, contained in all matter.

At the center of every atom is a nucleus, containing almost all of its mass and always carrying a positive electric charge. The positive charge attracts electrons and binds them, and jointly the two types yield an ordinary atom, electrically neutral, with no excess charge of either kind. Atoms like this build up you, me, and anything we can see on Earth. Red aurora over Virginia, 5 Nov.'01. Details here However, sunlight can separate electrons from atoms of the gas found in space (or in the upper fringes of the atmosphere), into negative free electrons and positive "ions", atoms missing an electron or more. And because that gas is so rarefied, it can take very, very long before an electron finds a vacant nucleus and recombines again. So, free electrons are plentiful there. Still, electrons moving at 1/10 the velocity of light, like those in the aurora, need a better explanation. We will get to that, by and by. The green and red colors are emitted by atoms of oxygen after they are hit by fast electrons. Each element emits its characteristic colors, and for rarefied oxygen, these appear to us green or red.

Typically, a delay of 0.5-1 second exists between collision and the emission (in this case--not in denser surroundings!), and that is why the rays of the aurora brighten and fade so slowly. The beam of electrons which "excites" the oxygen atoms may only last a small fraction of a second, but the afterglow persists 0.5-1 seconds or more. The Aurora and Magnetic Field Lines And what connects the pattern of the aurora to the region of the Earth's magnetic forces--the "magnetic field" of the Earth, as that region is known? For such a region, extending far into space, a convenient method is needed to describe it there. Such a method is provided by magnetic field lines, or as they were once called, "magnetic lines of force." Chances are you have seen a drawing of the field lines of a bar magnet. They fan out from one pole, bend around in big curves, and then converge on the other pole.

The magnetic pattern near Earth is like that, too--it is as if the Earth had a small (but oh so powerful!) bar magnet in its center: the lines fan out from the region near the south magnetic pole, reach their greatest distances above the equator, then converge again near the north magnetic pole. To define field lines more exactly, imagine you had a compass needle hanging in space, able to tell us the exact direction of the magnetic force, in 3 dimensions. Such a needle will always point in the direction of the magnetic field line at its location. North of the equator such lines converge towards the region near the north magnetic pole, just like those of a bar magnet. Birkeland and his terrella. Back to the aurora. Between 1895 and 1907 the Norwegian physicist Kristian Birkeland tried to study its behavior in a lab. Inside a glass vacuum chamber he mounted a sphere with a magnet inside--he called it "terrella," Latin for "little Earth"-- and directed towards it a beam of electrons. To his surprise and gratification, the magnet steered the beam right to a patch around the magnetic poles of his small sphere, producing there, as it hit, a visible glow.

He probably thought-- aha, so that is how it is done! It turned out (and I skip a lot) that negative electrons and positive ions alike are guided in space by magnetic field lines. They tend spiral around them, meanwhile sliding along them, like beads on a wire. Because Birkeland's field lines reached the terrella near its magnetic poles, that is where his electrons came down. Similarly magnetic field lines of the Earth guide electrons of the aurora to come down in the auroral zone. No wonder the rays of the aurora pointed along such lines! Each was produced by a ray of electrons, riding its own field line down to the atmosphere. But where did those electrons start from? The Sun's Corona and the Solar Wind Physical processes usually require a source of energy to drive them. Think of energy as a kind of money, paying for every physical process! Any object moving at great speed needs energy to do so--its "kinetic energy"--and if the aurora contains beams of electrons moving at 1/10 the velocity of light, something must have paid the price, must have provided the energy. Not surprisingly, it is the Sun. Indeed, why not?

After all, the Sun powers almost every process on Earth: the food we eat, the coal and gasoline we burn, the winds that blow and the rain which waters the land--none would exist without the energy provided by sunlight. With the aurora, however, it is not the light of the Sun, but something more subtle, the so-called solar wind. During a total eclipse of the Sun one can see the outermost layer of its atmosphere, the corona, a glowing halo around the darkened Sun. It turns out (by examining its light) that the corona is incredibly hot--about a million degrees centigrade, nearly 2 million Fahrenheit. Such extreme heat will tear electrons off any atom, turning the corona into a "soup" of free ions and free electrons, a strange gas known as a "plasma" which (among other things) conducts electricity. If you use fluorescent tubes, or have watched neon lights--it's the plasma inside them (not as hot as the corona) which carries their electric current and produces their light. The plasma of the corona is far too hot for the Sun's gravity to hold it captive.

Instead, it constantly expands away from the Sun and is blown off as the solar wind, filling the solar system and reaching Earth, and far beyond, past Pluto's orbit. The Earth's magnetic field, however, is an obstacle which the solar wind cannot penetrate. Like a river meeting a rock, it splits up and is diverted to flow around it. Around the Earth a cavity is formed, protected from the solar wind and known as the Earth's magnetosphere. And just as a rock in a river leaves a long shielded wake behind it, the Earth's magnetic space has a long tail on the night side--some call it the Earth's "magnetotail. " But even though the solar wind is kept out, it manages to transmit some electric energy to the magnetosphere, by brushing against it--in particular, to the tail region. Let me say here at once, the tail is where most electrons of the aurora seem to come from, which is why in Fairbanks the brightest aurora tends to occur around midnight--even in arctic winter when the sky is dark at most other times, too. At home, energy is carried by electric currents that flow from electric outlets to lamps, appliances and TV.

The energy of the solar wind also reaches the magnetosphere (at least in part) by means of electric currents. Satellites have observed those currents near Earth: they flow in and out of the auroral zone, along magnetic field lines--for the main circuit, in on the morning side of midnight, out on the evening side, the two branches connecting (since any electric circuits must be closed!) through the high atmosphere, which (as noted) conducts electricity. One might perhaps say that we are still searching where the plug is. The US Post Office honors the Polar Aurora (2007) Maybe the situation is not quite that dark. A lot is known. But the complete picture--where we can say "it has to be so, there exists no other way"-- that we still lack. The Radiation Belt One more detail is needed, a process called mirroring, without which the Earth might have neither aurora nor radiation belts. Radiation belts were discovered by the first US artificial satellites, Explorer 1 and Explorer 3.

In October 1957 the Soviet Union shocked the US by unexpectedly launching its two "Sputnik" satellites, while the "Vanguard," the US entry in the "space race," crashed in flames during launch, in full view of cameras. The sagging US prestige was redeemed a bit in early 1958 when instruments aboard the above satellites, designed and operated by the University of Iowa team under James Van Allen, detected a permanent belt of trapped ions, surrounding the Earth. They turned out to be protons--atomic nuclei of hydrogen atoms stripped of their single electron. Earlier it was claimed that electrons or protons tended to be guided by magnetic field lines, like beads on a wire. The ones which guided radiation belt particles had a typical shape--they came out of Earth's southern polar region, described a wide arc across the equator, and returned back to Earth near the northern pole. But if the analogy with beads on a wire were complete--wouldn't trapped particles slide to the ends of those wires, then hit the Earth and get lost? Quite true--except the analogy is not perfect.

The ends of those lines also experience a much stronger magnetic force, being much closer to Earth than other parts, and that can be shown to repel those "beads." By being repelled from regions of strong magnetic force, trapped electrons and ions avoid reaching the atmosphere. Instead of getting absorbed, they get "mirrored" back and forth--in some cases, for years! Electrical Currents of the Aurora The same process is also essential to the aurora. We already mentioned large electric currents flowing from the tail into the polar regions and back again, flowing along magnetic field lines, earthward on the morning side of midnight, outbound on the evening side (for the main circuit--a secondary one also exists). They were first mapped in 1973 by two US scientists, Al Zmuda and Jim Williamson--not with a well-supported space research mission, but using a small experiment and a bummed "piggy-back" ride with a navigational satellite of the US Navy. Those currents are now known as "Birkeland currents, " honoring the Norwegian who first shot electron beams at a magnet in vacuum.

The currents along magnetic field lines in space turn out to be carried almost entirely by electrons--descending towards Earth west of midnight, rising up again east of it (being negative, their flow opposes that of the current). In light of what was noted a little earlier about the "mirror force" which repels trapped particles from regions of intense magnetic field, one may well wonder how this force affects the flow of electrons which carry those currents. Where electrons move upwards, the mirror force is no problem--on the contrary, it helps push the electrons away from Earth, towards weaker magnetic fields. However, it is a different story where electrons come down. With radiation belt particles, the mirror force keeps them safely away from the atmosphere--but here, those electrons better reach the upper layers of the atmosphere (where the current can continue horizontally to the other branch). If not, the electric circuit remains unclosed! So what happens? In our homes no electric currents will not flow unless a sort of electric pressure pushes them on--a pressure we call "voltage." In the home it measures 110 volt, average value (actually it fluctuates, being AC). Space currents also have a voltage pushing them, something like 40,000 volts.

In the home, if an obstacle is placed in the circuit--an electric resistance, such as a lightbulb--the voltage concentrates there to helps push the current through the bottleneck. Same thing in space! There the bottleneck is the mirror force at the ends of the field line, and to overcome it, something like 5000-15,000 volts are concentrated there, pushing those electrons through. The voltage speeds them up to about 1/10 the velocity of light, and when they hit the top of the atmosphere, they produce a bright glow. That is the polar aurora! Substorms and slingshots an imaging camera aboard DE-1 Well--at least, one kind of aurora. Other kinds exist, too. The magnificent "ring of fire" around the magnetic pole, displayed on images from satellites (like the one here, on the left), is actually a different kind. It is too faint for the eye to see, but easily seen by spacecraft. But the bright arcs we see from the ground are usually associated with electrical currents flowing from Earth into space--to somewhere in space. (It may be confusing, but age-old convention has it that currents flow from (+) to (-).

Therefore, when negative electrons come down, the currents they carry flow upwards.) To recapitulate, the electrons must overcome the "mirror force" of the strong magnetic field near Earth, which tries to keep them out, and they do so with a concentration of voltage. And a proof exists. The mirror force is strongest near Earth, where the intensity of the magnetic field is greatest, so one expects the voltage to be greatest there, too. And since that voltage is the source of energy of auroral electrons, they should only acquire it pretty close to Earth. Indeed, satellites show that those electrons are only speeded up near Earth, in the last 2-5000 miles before they hit. Not all such currents are directly connected to the solar wind. A very bright and violent type of auroral arcs--associated with the "auroral substorms" mentioned before--seem to be produced (in part or totally) inside the magnetotail. In such cases the tail behaves a bit like a slingshot. The solar wind pulls its field lines and stretches them to the limit.

Then, when they get released and bounce back, they create (for a while--say half an hour to an hour) strong electric currents, and many, many auroral electrons. Those sunspots The Sun gives out sunlight, and its hot corona produces the solar wind, the source of the aurora's energy. But the Sun is also magnetic--with a large-scale polar magnetic field (a bit like the Earth's), as well as sunspots, compact regions of concentrated magnetism. These too influence the aurora--through the interplanetary magnetic field, carried out from the Sun by the solar wind (won't go into that), and through occasional magnetic storms. Most people have heard about sunspots--dark markings on the sun (a sunspot group is pictured on the left). Their number rises and falls with an irregular cycle of about 11 years, and some people have speculated (not too convincingly) that it matches the rise and fall of climate, the stock market, warfare and more. That cycle was first noted by an amateur astronomer in 1843--more than two centuries after sunspots were first discovered (by Galileo and others).

Astronomers had missed it completely, leaving it to Heinrich Schwabe, a German pharmacist and amateur astronomer. Schwabe searched for a planet orbiting close to the Sun inside the orbit of Mercury, tentatively named "Vulcan." You only see stars at night, so to detect one very close to the sun, you either need a total eclipse of the sun, or else you look for a dark spot crossing in front of the Sun's disk. Schwabe looked for that spot every sunny day, and to distinguish it from sunspots (which rotate with the sun and move much more slowly), he kept tabs on sunspots as well. In 17 years he found no planet, but discovered instead that the number of sunspots rose and fell in a regular cycle. As noted, sunspots turned out to be intensely magnetic. Associated with them are outbursts of magnetic energy, which fling fast clouds of plasma--faster than the usual solar wind--in all directions. One sign of outbursts are flares, sudden brightenings which also create a flood of x-rays. (These are not dangerous to astronauts, but the fast protons ejected at the same time can be).

Another are "Coronal Mass Ejections," big bubbles of gas blown off the sun, reported in 1973 by astronauts on the space station "Skylab." Whatever causes them, these clouds sometimes arrive near Earth and agitate its magnetosphere in a magnetic storm. The result, as noted, are bright auroras, pushed to locations much further from the poles. That is why, usually in years around the peak of the sunspot cycle, many more people get a glimpse of the polar aurora. Artificial auroras All the above is just a short and superficial overview of the science of the polar aurora--and I won't even try address the lore and literature. Let me conclude with two somewhat exotic aspects--artificial auroras and auroras on other planets. Auroras, as was said, are caused by beams of electrons hitting the high atmosphere. So, if we mount an electron gun on the space shuttle or on some other spacecraft, and aim it down--can we create aurora? In principle, yes, but in practice it's not easy to match Mother Nature. Remember, all auroras displays are at least 60 miles above our heads.

It takes a lot of power to create a glow visible at that distance--especially, one as large as an auroral arc!. Experiments have been carried out--notably, the French-Soviet "Arkad" experiment above northern Russia (also some by the US), and spots of light were detected, but it took sensitive instruments to see them. However, other more drastic ways also exist--such as exploding a nuclear bomb above the atmosphere, since a bomb produces great numbers of fast electrons. Such explosions were suggested by an unconventional Greek scientist named Nicholas Christofilos. He started out as an engineer designing elevator systems, but his real interest lay in magnetic fields and in the motion of ions and electrons in them. His interest led him to discover an important idea in the design of accelerators for nuclear research, known as "strong focusing." He wrote to Columbia University in the US, describing what he did, but scientists there did not pay enough attention to the ideas of an elevator engineer in Athens. They sent a polite reply and dropped the idea. A few years later, a Russian came up with a similar concept. However, the US Air Force remembered Christofilos and invited him to this country.

Because he was interested in the trapping of particles, Christofilos proposed creating an artificial radiation belt around Earth, by exploding a small nuclear bomb above the atmosphere. No one suspected the existence of a permanent natural radiation belt, but some small nuclear bombs had been exploded by the US Air Force high in the atmosphere, near Hawaii. They created glows in the sky with the colors of the aurora, and people in Honolulu oohd and aahd over them--I have a dim memory that "Life" even ran a picture. So Christophilos prepared his bombs (to be flown on a rocket), while Russia prepared its Sputnik and Van Allen got ready for Explorers 1 and 3. Sputnik was launched in October 1957, Explorer 1 was launched on the last day of January 1958, the newly discovered radiation belt was described that May, and the 3 bombs of "Project Argus" were exploded in August and September 1958, above an empty stretch of the South Atlantic. No observation broke the secrecy of the project, and no newspaper told about it at the time.

But the bomb's electrons were guided by their magnetic field lines to their other end, near the Azores Islands, and produced a bright aurora which was seen by observers aboard ships deliberately stationed there. The "artificial radiation belts" from the bombs lasted about 2 weeks and were monitored by Explorer 4, built by Van Allen for that purpose. Four years later the US Air Force decided to repeat the experiment on a grand scale west of Hawaii, using a hydrogen bomb, about 1000 times more powerful. This time the auroral electrons were guided towards Samoa--close to the equator, in a region where auroras had never been seen. But the explosion was too close to the equator, in a region where trapping was much more efficient. The radiation belt hung around for years, not weeks, and quickly destroyed 3 satellites (including a British scientific satellite NASA had just graciously launched), by degrading their solar panels and depriving them of power. The Soviet Union also exploded H-bombs in space, but the following year brought the international test ban and all such experiments ended. Other Planets NASA spacecraft have shown that the giant planets--Jupiter, Saturn, Uranus and Neptune--are all magnetic, and do have radiation belts.

Jupiter, the biggest, outdoes them all--its "central magnet" is about 20,000 times stronger than ours. It also has auroras, photographed by the orbiting Hubble telescope (see here for a recent picture ). Their origin (at least that of the stronger ones) is interesting. As noted, Earth's aurora is associated with electric currents, and so is Jupiter's. Jupiter has 4 large moons (as big as ours or bigger), and the innermost one, Io, is a strange and hellish place, with its interior heated by tides, producing sulfur volcanoes and molten lakes. As a result, it (or the atmosphere around it) conducts electricity, and as Jupiter's magnetic environment rotates past it (just as the solar wind flows past Earth), electric currents are produced along the field lines linking it to Jupiter. We know about those currents because Voyager 1 flew close to them in 1979 and observed the magnetic pattern they produced. And we know the observed auroras are due to those currents, because the structure of Jupiter's magnetic field has been mapped.

Using that mapping to trace magnetic field lines from Io to the surface of the planet, one arrives exactly at the spots where auroras are seen. Aurora on 6 January 1998 (Dick Hutchinson ©) One could go on and on, but even this quick tour should prove that the polar aurora is much more than a pretty show of lights. It also provides insight into the way physics and nature affect the space region around Earth. Aurora Borealis Yukon-Northern Lights | Nature Tours Yukon Northern Lights - Aurora Borealis in Yukon When is the best time to watch for Aurora Borealis in Yukon? In Yukon Autumn and Winter are generally good seasons to see the Northern Lights. The long periods of darkness and the frequency of clear nights provide many good opportunities to watch the Aurora Borealis . Usually the best time of night (on clear nights) to watch for Northern Lights is local midnight (adjust for differences caused by daylight savings time). Where is the best place to watch the Northern Lights? The best place to see the Aurora in Whitehorse is outside town, so the lights of the town do not interfere with the visibility of the Aurora Borealis.

Nature Tours of Yukon specializes in "The Great Yukon Aurora Hunt", were we take you to the best spots to see the northern lights. Because the phenomena occurs near the magnetic poles, the best places to watch the Northern Lights (in North America) are in the Yukon, Nunavut, Northwest Territories and Alaska. Photography Taking good pictures of the Northern Lights is not easy, since they're fast-moving, often faint and against a pitch-dark background, all of which befuddles consumer point-and-shoots. Here's what you need for a sporting chance: A camera that supports manual exposure (5 to 40 seconds). A fast lens (aperture f/2.8 or better) Fast film (800 ASA or better), or equivalent ISO setting on a digital camera A tripod to hold the long exposure Cable release or self-timer to trigger shots without stirring the camera Legends of the Aurora Borealis. Many cultural groups have legends about the Aurora Borealis or Northern Lights. From dragons to dancing souls, cultures throughout the world have attempted to explain the swaying lights in the night sky through legends and myths.

From northern First Nations beliefs that related the Aurora Borealis with life and death, to ancient Chinese cultures that created the earliest dragon legends from the Northern Lights, the aurora have affected cultural beliefs from the moment they were perceived. A common Inuit belief was that the auroras were the souls of the departed on their way to the afterlife, while other Inuit thought that they were the souls of unborn children. Eskimos living in the Hudson Bay area held that whistling at the northern lights would cause them to move towards the sound while clapping would jolt it away. Others in regions of Greenland and some parts of Canada believed the lights to be departed souls attempting to contact living loved ones. What are Northern Lights? The bright dancing lights of the aurora are actually collisions between electrically charged particles from the sun that enter the earth's atmosphere. The lights are seen above the magnetic poles of the northern and southern hemispheres. They are known as 'Aurora borealis' in the north and 'Aurora Australis' in the south.. Aurora Borealis displays appear in many colours although pale green and pink are the most common. Shades of red, yellow, green, blue, and violet have been reported.

The lights appear in many forms from patches or scattered clouds of light to streamers, arcs, rippling curtains or shooting rays that light up the sky with an eerie glow. Northern Lights can be seen in the northern or southern hemisphere, in an irregularly shaped oval centred over each magnetic pole. The lights are known as 'Aurora borealis' in the north and 'Aurora Australis' in the south. Scientists have learned that in most instances northern and southern auroras are mirror-like images that occur at the same time, with similar shapes and colours. What causes the Aurora Borealis? The Northern Lights are actually the result of collisions between gaseous particles in the Earth's atmosphere with charged particles released from the sun's atmosphere. Variations in colour are due to the type of gas particles that are colliding. The most common Aurora Borealis colour, a pale yellowish-green, is produced by oxygen molecules located about 60 miles above the earth. Rare, all-red auroras are produced by high-altitude oxygen, at heights of up to 200 miles. Nitrogen produces blue or purplish-red aurora.

The lights of the Aurora generally extend from 80 kilometer (50 miles) to as high as 640 kilometer (400 miles) above the earth's surface.

Question: What is the Southern equivalent of the Aurora Borealis?
Answer: Aurora Australis