Northern lights and winter tent. This is a winter tent of the Sami, the indigenous people of Lapland, an area that extends across northern Scandinavia and north-western Russia. The northern lights (aurora borealis) is a coloured light display (here, green) that is visible in the night sky, usually only at high latitudes. It occurs when charged and energetic particles from the Sun (the solar wind) are drawn by Earth's magnetic field to the polar regions. Hundreds of kilometres up, they collide with gas molecules and atoms, causing them to emit light. Photographed in January, near Abisko, in Swedish Lapland.