The Aurora, or the Northern Lights are coloured lights seen above the magnetic poles of the northern and southern hemispheres. They are actually the result of collisions between gaseous particles in the earth’s atmosphere with charged particles released from the sun’s atmosphere. Variations in colour of the Northern lights are due to the type of gas particles that are colliding. The lights are known as ‘Aurora Borealis’ in the North and ‘Aurora Australis’ in the South. The term ‘Aurora Borealis’ was coined by Galileo in 1619, from the Roman goddess of the dawn and the Greek name for the north wind.
Due to extremely high temperatures, there are frequent and explosive collisions between gas molecules above the surface of the sun. Free electrons and protons are thrown from the sun’s atmosphere by the rotation of the sun and escape through holes in the magnetic field of the sun. Due to the solar wind, these electrons and protons are blown towards the earth. Most of these particles are deflected by the earth’s magnetic field, but some of them enter the earth’s atmosphere where the magnetic field is weak.
These particles collide with the gaseous particles present in the earth’s atmosphere, emitting light that we perceive as the dancing lights of the North and the South. The lights of the Aurora generally extend from 80 kilometres (50 miles) to as high as 640 kilometres (400 miles) above the earth’s surface.
The most common color of the Aurora is pale yellowish-green, which is produced by oxygen molecules located about 60 miles above the earth. Although rare, red auroras are produced by high-altitude oxygen, at heights of up to 200 miles. Nitrogen produces blue or purplish-red aurora.