Northern Lights

Description

The aurora 'sings' when you hear it under the right conditions. It forms when electrons and protons stream down along Earth's magnetic field and strike oxygen and nitrogen high in the atmosphere, which give off the energy as light. The usual green glow comes from oxygen about 100 km up. The crackling some hear on calm, cold nights may come from electrical discharges about 70 metres above the ground, a Finnish researcher has proposed.