Aurora Borealis (Northern Lights) are a visible glow in the northern sky at high latitudes and are named after the Roman goddess of dawn, Aurora, and the Greek name for the northern wind, Boreas. The equivalent in the southern sky is the Aurora Australis.
Aurora are caused by the collision of high energy ions (charged atoms as a result of one or more electrons being removed) from the solar wind with atoms in the upper atmosphere of Earth. The solar wind comprises of ions emitted by the Sun, these are caught by the Earth’s magnetosphere (effect of Earth’s magnetic field) and directed towards the magnetic pole where they collide with atoms. These excited atoms then either lose energy through the emission of a photon (light) or by collision with another atom. Excited oxygen emits either green or brown-red light, excited Nitrogen emits blue or red light.