How Do Aurorae (Northern and Southern Lights) Occur?
As solar particles from an incoming Coronal Mass Ejection (or CME) move into Earth’s magnetosphere they travel around to its back side — or night side, since it is on the opposite side from the Sun — along the magnetic field lines.
When these magnetic field lines reconnect in an area known as the magnetotail, energy is released and it sends the particles down onto Earth’s poles, and sometimes even lower latitudes. As the particles bombard oxygen and nitrogen in the upper atmosphere, the atoms release a photon of light that we see as the beautiful colors of the aurora.
(via: NASA Solar Dynamics Observatory)
