Breathtaking Phenomena -- Aurora Australis and Aurora Borealis
The Southern and Northern lights


The origins of the lights: The Myths

    The Intuits of Hudson Bay believed the sky was a dome with holes. They believed on the other side of the dome were the heavens. The spirits of the dead were to go out of the earth through the holes and enter the heavens. To guide the spirits into the heavens, the torches (auroras) guided them.

    In Middle-Age Europe, the northern lights were thought to be reflections of heavenly warriors. As a kind of posthumous reward, the soldiers that gave their lives for their king and country were allowed to battle on the skies forever. The northern lights were the breath of these brave soldiers as they resumed their fight in the skies.


    It was also believed that in Finnish they are called "revontulet", which means "fox fires" a name derived from an ancient fable of the arctic fox starting fires fire or spraying up snow with its brush-like tail. In English, foxfire is a luminescent glow emitted by certain types of fungi growing on rotten wood.

    Some of the elders believed that the "lights in the sky" were the highways upon which the souls of the dead traveled to be with the gods. Others thought that the ribbons and streamers portended great events, both evil and good.


The origins of the lights: The Science

    The Northern and Southern Lights is formed when the sun gives off high-energy charged particles (also called ions) - during periods of high sunspots activity-that travel out into space at speeds of 300 to 1200 kilometers per second, taking a few days to reach the Earth. A cloud of such particles is called plasma. The stream of plasma coming from the sun is known as the solar wind. As the solar wind interacts with the edge of the earth's magnetic field, some of the particles are trapped by it and they follow the lines of magnetic force down into the ionosphere, the section of the earth's atmosphere that extends from about 60 to 600 kilometers above the earth's surface. When the particles collide with the gases in the ionosphere they start to glow, producing the spectacle that we know as the auroras, the northern and southern lights. The aurora colours are classified as follows: Green with top fringes of Red, Green with red bases, Green, Red, Blue or Violet.

           

The frequency and intensity of occurring aurora correspond to the number of sunspots as shown:

    From the graph, we can see that the frequency and intensity of occurring aurora are especially high at periods of solar maximum (when a large number of sunspots are observed). On the other hand, during which when the sun is relatively inactive - when almost no sunspots can be observed during solar minimum - aurora is uncommonly seen.


Natural Fireworks in the Sky - A Wonder of Nature

    The prime viewing locations for the Northern Lights, aurora Borealis, include Fairbanks, Alaska, and many locations in eastern Canada for the northern hemisphere. In Europe, Iceland and northern Scandinavia see most of the aurora. In the southern hemisphere, the aurora frequents uninhabited regions, making sightings of the Southern Lights, aurora Australis, more rare than the Northern Lights, aurora Borealis. An interesting fact is that when aurora occurs, the Northern and Southern lights should have symmetrical patterns! Well, who actually sees it?

September and March and especially at during the equinoxes, are the most frequent months and times for aurora. This period is usually at the time when Earth’s orbit falls in the zone of solar activity.
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    Aurora is often bright enough to be seen with the naked eye. They often take the form of curtains of light in which the folds rapidly move and vary in brightness. Often the curtain rests on an arc of light. The colour given off by the aurora depends on the type of gas in the atmosphere: Oxygen gives off green and red colours, Nitrogen gives off red colour, etc.

    The most active region of the aurora oval typically becomes visible around local midnight. This region is also the widest part of the oval in the north-south direction, so your best chance of seeing aurora is around local midnight. (Note that this is astronomical midnight, which may be an hour or two different from civil or "wall clock" midnight due to daylight savings time or other peculiarities in your time zone). Although spectacular aurora displays due to geomagnetic disturbances may be seen at any time when the sky is dark, but they are relatively unpredictable. Under average conditions, observations around local midnight are most likely to yield results.

           

Weather and light pollution affect the chances of seeing aurora.
You cannot see aurora if the sky is overcast; even a slight haze may prevent you from seeing the aurora, more so if the sky illuminated by light pollution from a nearby urban area. So, to view aurora, do choose a good location, a good time, and when the sun is active. The main condition is when there are lots of sunspots!
   


Resources: SpaceWeather.com, Sept. 29 - Oct. 3, 2001 Aurora Gallery   
Virtual Finland, Aurora Borealis - Northern Lights   
Alaska Science Explained!   
Aurora   

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