The Aurora Borealis is one of the most unusual and beautiful phenomena our amazing planet Earth has to offer. But what exactly is it that has caused people to stare in wonder at the skies and has been the stuff of myths and legends?
The Aurora Borealis is found in the Northern Hemisphere and is caused by particles from the sun's solar winds meeting the magnetic field surrounding the Earth. The solar winds blast towards Earth at around 1 million miles an hour and, once they've left the sun, take a journey of around 40 hours to get to Earth. These high-speed winds are drawn towards the magnetic fields that the Earth produces from its core. As the solar winds approach Earth, they come into contact with different elements and, depending on their altitude, the reaction results in the eerie dancing lights in the sky.
Why are there different colored lights?
The Earth's upper atmosphere contains atoms of oxygen and nitrogen, in layers, from altitudes of 20 to 200 miles above the Earth's surface. The Aurora's colors depend on which atom is struck and at which altitude they meet. For example:
- Oxygen, up to 150 miles in altitude = Green
- Oxygen above 150 miles in altitude = Red
- Nitrogen up to 60 miles in altitude = Blue
- Nitrogen above 60 miles in altitude = Purple/Violet
How do the lights 'dance'?
The electrical forces from the solar winds and Earth's magnetic forces constantly interact with one another in shifting combinations allowing the swathes of color to move and 'dance' in the sky.
The Aurora Borealis can be seen at the magnetic North Pole while the Aurora Australis occurs at the magnetic South Pole. Sunspot activity seems to influence this strange phenomenon and can allow the lights to move further south. 2012 will be a good year to view the Northern lights, as sunspot activity will be particularly active. These active periods usually occur within 11-year cycles and NASA has predicted record northern light activity for Winter 2011/12. It may even be the strongest show of lights for 50 years!
It's not just Earth where Aurora's can be viewed. Saturn, Jupiter and Uranus have all been found to have their own display of lights. So long as a planet has a magnetic field and an atmosphere, Auroras should be seen.