The aurora borealis (the Northern Lights) and the aurora australis (the Southern Lights) have always been on people's wish list to visit, but how they actually form is a mystery to many people.   Both of the auroras surrounding the north and South Pole occur when highly charged electrons from solar wind (see next post) interact with elements within our atmosphere. These particular solar winds can be up to speeds of 1 million miles per hour! They then reach earth some 40 hours since leaving the sun. They follow the lines of the magnetic field (much like you would see on a diagram). The solar winds then flow through the earths magnetosphere, this is a teardrop shaped area of highly charged electrical fields.



When the electrons enter the earth's paper  atmosphere they come across atoms of oxygen and nitrogen at altitudes from 20 to 200 miles above the earth's surface. The colour of the aurora depends on which atom is struck and the altitude at which this happens. 

  • Green - oxygen, up to 150 miles in altitude
  • Red - oxygen, above 150 miles in altitude
  • Blue - nitrogen, up to 60 miles in altitude
  • Purple/violet - nitrogen, above 60 miles in altitude

The magnetic and electrical forces react with each other, which creates the "shifting" combinations of colours and patterns, some people might say that the auroras "dance". The auroras then move along with the atmospheric currents, which can be as high as 50,000 volts. To put this into context circuit breakers in your home start working when the current reaches 120 volts. 

The northern or southern lights generally happen along the "auroral ovals", these are at the centre of the magnetic poles and they roughly coincide with the Arctic and Antarctic circles. They can however, appear further south when there is alot of sunspots, these occur in a rough 11 year cycle the last happened in 2011/12 where many people enjoyed the northern lights outside their normal range.