Aurora Borealis and Star Trails, Hammerfest, Norway

 

Aurora Borealis and Star Trails, Hammerfest, Norway

Each appearance of the northern lights is unique. Often you see three green bands across the night sky. Or the lights come as flickering curtains or rolling smoke. The colour is a luminous green, often with a hint of pink along the edge, and occasionally with a deep violet centre.

It is the sun that lies behind the formation of the auroras. During large solar explosions and flares, huge quantities of particles are thrown out of the sun and into deep space. When the particles meet the Earth's magnetic shield, they are led towards a circle around the magnetic North Pole, where they interact with the upper layers of the atmosphere. The energy which is then released is the northern lights. All this happens approximately 100 kilometres above our heads.