What are the Auroras or Northern Lights?

The Northern Lights or Aurora Borealis are discharged particles from the sun that pass through the magnetic shield of earth and create light when they mix with atoms and molecules such as nitrogen and oxygen gases on entering into the earth's atmosphere. These particles travel 149 million kms or 93 million miles through space towards planet earth being drawn towards the earth's magnetic north and south polar regions.

Inside the Sun

The brighter areas are sun spots- portals where gases escap photo : NASA

If the sun was hollow earth would fit 333.000 times inside it's mass, at it's core temperature the sun is around 27 million degrees and is made up of mainly hydrogen gas. It behaves similar to a pot of boiling water, as water boils to the surface of a pot in a mushroom form it cools by letting off heat and then returns downward to be reheated again. As the sun's burning gases go through this similar process some particles escape from portals on the surface called Sun Spots and enter into space as flying plasma particles named Solar Wind.





Sun Spots
The sun has many magnetic fields that emerge from within the sun forming loops that protrude out from the

Explosions shaped by the suns magnetic fields blast through sun spot portals. photo: NASA

surface, like spaghetti in boiling water. As the sun rotates these magnetic fields get distorted, twisted and knot together where they burst and a sun spot is born. They usually appear in pairs and can vary in size the largest being several times the diameter of earth. These sun spot portals are responsible for the solar wind projections.






The earth's protective shield

The Solar Wind travels at an extraordinary speed covering the 93 million miles to earth in a staggering 2 to 3
days. It's around 1000km per second or a million miles per hour. Normally the earth can deflect such space matter easily because of earth's magnetic field which acts as a protective shield (kind of like water flowing around a stone in a river). However in high activity cycles called Solar Flares the increased particles travel through space and bombard our magnetic shield to deform it slightly in shape. Some of these particles penetrate our magnetic field and come into contact with different gases which produce the aurora northern lights that we see.

The colors of the Aurora
As the solar wind particles enter the earth's atmosphere they collide with molecules of nitrogen and
oxygen which relinquish their agitated energy in the form of light. Oxygen typically produces green and yellow light while nitrogen produces reds, violets and occasionally blue. Violets typically form a boarder around curtains of green aurora shapes in lower altitudes.






The Aurora shapes
The Northern Lights can be both static and dynamic throughout the night sky. During periods of minimum solar flares the aurora can produce a blanket strip type of light without much definition or varying color. However during periods of strong solar flares the light becomes dynamic which swirls, dances and even races in curtains and columns in a random path throughout the sky. The colors merge and diverge from greens to reds and violets. The sight is spectacular beyond belief.

When and where to see the Northern Lights
Where - The auroras can be seen at the polar regions of the north and south pole. However the south pole is
largely inaccessible to human life and the north polar region is easily accessed from Europe. The best chance you have is to visit the latitudes in the Arctic Circle from 68 to 74 degrees. Alaska and parts of Canada are also good for sightings but due to the great vast open expanses of these countries it can make a visit to them an real logistical expedition. Norway and the northern parts of Scandinavia are easily accessible and provide one of the best places in the world to witness auroras or northern lights in Norway.

When - during the winter season as this is due to the low light pollution and crystal clear air. The auroras occur all year round but we need nightfall to see it as the sun's light during the day overpowers the northern lights. The Aurora activity seems to be at it's most active late evening between 10pm and 1am but can be seen in the afternoons during the polar winter above the Arctic circle.

The sun's cycle - sun spots increase and decrease on an 11 year cycle. Since records began in 1749 there have been 22 full cycles. 2009 / 2010 is in the  23 cycle and the next solar maximum will be 2013. During periods of solar maximum the aurora can be seen far below the Arctic Circle and as far as central Europe and intense northern lights activity can interfere with radio, satellite and GPS signals sometimes shutting down networks.  The sun rotates around it's own axis once every 27 days so after a period of high northern light activity has taken place in Northern Norway it is common that after 27 days there will be another strong display of the aurora as the sun spots once again face earth.
The world's climate and the sun
The world's climate is also believed to be influenced by these solar cycles as past planet history has shown that warm and cold cycles may be linked to periods of solar maximum and minimum cycles but the total impact is still not fully understood - but I will update as I find!

Your chances of seeing the Aurora - northern lights
During autumn and winter there is a strong chance to see the aurora during the evenings. Periods of high pressure weather systems are best as they present clear cold skies, a low moon and no urban lighting is an advantage. A close look on the satellite observations of the sun are important and it is possible to forecast the aurora activity within three days accuracy as NOAA polar satellites monitor the aurora activity and solar storms on the sun.
Graham Austick.