Northern lights
Polar lights are called northern lights (aurora borealis) at the northern hemisphere and southern lights (aurora australis) at the southern hemisphere.Their origin is a solar storm, which flings mainly electrons with more around 300.000.000 m/s among others in direction of the earth. The magnetic field causes the electrons in direction of the poles. Cloth to them the earth magnetic field is orientated in a way that the electrons can invade into the atmosphere. Here the oxygen and nitrogen atoms become excited (which means that one electron of an atom gots more energy for a short time and stays a bit more far away from the core). After a short time it relaxes to his ground state (typical state) by emitting a photon of a specific wavelength, which we see as coloured light. By an extinction of oxygen atoms in around 100 km height the light appears green for us. Oxygen atoms in around 200 km height are creating red lights and nitrogen atoms causes the atoms to emit violet to blue lights.
