Sparked by charged particles that had been ejected by the sun three days earlier, an aurora borealis streaks into view in the wee hours of September 15 over Ersfjord, Norway. The same night, similar shows enlivened skies over northern Canada and elsewhere in Europe.
When a charged-particle cloud enters the upper atmosphere of Earth, it smashes into and breaks up gas molecules, creating the northern lights (or in the Southern Hemisphere, the southern lights).
"Like gas inside a neon sign, as the atoms smash together they begin to glow—producing a great light show," Manuel said.
The colors a sky-watcher sees depends on what type of gas is being hit and how high it is. For example, the green aurora pictured was the result of oxygen-atom collisions about 60 to 120 miles (100 to 200 kilometers) up.
(Related: "Light Pillar Pictures: Mysterious Sky Shows Explained.")http://www.nationalgeographic.com/