The Northen Lights or Aurora Borealis is a natural phenomenom occuing in the night sky at the top of the Northern Hemisphere.
Lights, similar to that of a sunset in the sky at night but ocasionally in arcs or spirals and usually folloing the earth's magnetic field. Most often light green in colour but also a sometimes a variety of other colours
Simply: The Aurora Borealis is caused by charged particles which are ejected from the sun. When the particles reach the earth, they collide with gas atoms in the earth's atmosphere causing them to energise which results in a spectacular multi-coloured light show.
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The top of the northen Hemisphere, Alaska, Canada, South Greenland, Iceland, north Norway, north Russia and north Sweeden. Away from any cities, or lights of any kind in a remote place with a clear night sky.
The Aurora is at it's peak in September and in March but also in October and April. You can best see the lights at around midnight