Aurora Borealis- The "Northern Lights"

A gorgeous display of aurora bands

The Aurora Borealis, or Northern Lights, is a large scale phenomenon distributed along a narrow band encircling the North Pole. Much of the central NWT mainland lies within the auroral zone, in which the Lights are most often seen.

The Aurora Borealis is an electrical discharge powered by a "generator" composed of the solar wind and the earths magnetosphere. The solar wind, a plasma of high-speed charged particles streaming out from the suns corona, acts as the conductor. As the solar wind blows towards the earth, a cavity called the magnetosphere is formed when the plasma meets an invisible obstacle of the earth's magnetic field. Magnetic field lines above the polar region fan out in the cavity and are connected to magnetic field lines of the solar wind across the boundary of the magnetosphere. The solar wind blows around this boundary and across the connected field lines, generating power up to 1,000 billion watts. The current is carried mainly by electrons. When these electrons collide with atoms and molecules in the upper atmosphere, they emit their characteristic lights. The process is comparable to neon lighting.

The Aurora Borealis has practical consequences as well as aesthetic pleasures for residents of northern Canada. The Aurora disturbs the polar ionosphere, causing disruption of radio communications and navigational difficulties. Satellite performance can be affected by the electrical discharge and associated geomagnetic disturbances can change the direction of compass needles. Variations in the intensity of the ionosphere current can induce electric currents in long conductors on earth such as power line systems, telegraph wires and oil and gas pipelines causing transformer malfunction, power outages and other damage.

Galileo, in the seventeenth century, was the first to call this display the "Boreale Aurora", or "Northern Dawn".

The aurora appears as a doughnut-shaped ring around both north and south magnetic poles. These rings are symmetrical, and occur at the same time.

The aurora is in place day and night, all year round. However its colours, soft as starlight, are not visible to human eyes during daylight and twilight.

There is generally a 27 day cycle between the most brilliant auroras, tied to the sun's 27 day revolution period. There is also a longer 11 year cycle in which the northern lights diminish and increase, becoming visible even in mid-latitudes. 2002 and 2013 will be peak years.

Strong auroras with their magnetic disturbances can cause problems in the north - and beyond. Radio signals become broken-up and unintelligible, whilst pipelines and power transmission lines act as conduits for electrical currents created by fluctuating magnetic fields.

The Aurora Borealis is usually blue-green or yellow-green in colour, sometimes edged with pink. Deep red auroras are very rare, and can be visible far to the south. They are caused by an unusually heavy bombardment of particles from the sun, acting upon the oxygen in our atmosphere. In the past, such blood-red displays were perceived as evil omens, and terrified peoples of many cultures.

While people often report hearing swishing sounds in conjunction with the lights, no such recordings have ever been made. Many researchers are skeptical of such sounds. Others believe they may be related to radio waves or static electricity that accompanies auroras.