When flying from Seattle to London, I looked out the window and saw the Aurora Borealis. These beautiful waves of light are caused by the violent collisions of charged particles with gas molecules in the Earth’s ionosphere. When the sun emits charged particles that flow toward the Earth as solar winds, the Earth’s magnetic field deflects the particles towards the poles. The charged particles transfer energy to gas molecules’ electrons, causing the electrons to shift into a higher energy level. The electrons then crash back into the more stable, lower energy levels, releasing a photon of light. This is essentially the same process that allows neon lights to shine, only at a much larger and more impressive scale.

The different colors that are seen in the northern lights are due to the different gas molecules in the ionosphere. The vivid green that I saw out of the airplane window results from particles interacting with oxygen at altitudes of around 100-300km, the plane I was in was flying at an altitude of around 12km. Pink is caused by nitrogen gas at roughly the same altitude. Red is caused by oxygen at altitudes of 300-400km.