This video of an aurora was created from still photographs taken by astronauts aboard the International Space Station as they passed over the Indian Ocean in early March.
Almost hard to believe it’s real, isn’t it? Phil Plait of the Discover blog Bad Astonomy, explains auroras like this:
The lights are caused by atoms in the upper atmosphere getting hit by subatomic particles blasted out by the Sun, caught by our Earth’s magnetic field, and funneled down into our air. These particles dump energy into the atoms, moving the electrons up in energy (called excitation). The electrons then jump back down, emitting light in the process (de-excitation). As I said in an earlier post, it’s like needing energy to jump up stairs, but releasing it as you jump down.
Different atoms have different energy levels for the electrons — think of it as more or less spacing vertically between steps in a staircase — so the energy emitted is different, resulting in different colors emitted. That’s why we see green, red, purple… they come mostly from oxygen and nitrogen in the air. So as the magnetic field fluctuates, the particles are sent shooting down in different places, giving the appearance of motion while the atoms themselves don’t move.
(If you’re interested in astronomy, you should check out the Bad Astronomy blog: Bad Astronomy | Discover Magazine)
For a discussion of auroras that focuses more on the magnetic fields themselves, see this page from The Exploratorium: Auroras: What makes them happen?