Composite photo showing the Northern Lights (Aurora Borealis) seen from Vik beach in Iceland. Vik beach, known locally as Reynishverfi, is famous for its black volcanic sands. The Northern Lights are caused by particles from the Sun - electrons mainly but also protons ??exciting or ionising oxygen and nitrogen in our atmosphere as they flow along our planet's magnetic field lines. The glow occurs when the atoms recombine or become de-excited.