From Doug Wheelock’s Twitpic page, an astronaut on the International Space Station (ISS), comes this brilliant image of the Southern Lights (Aurora Australis) as seen from the ISS.
The northern (Aurora Borealis) and The southern (Aurora Australis) are caused when the charged particles (ions) from the Sun hit the Earth. The ions from the Sun excite the electrons of the atoms in the atmosphere which in turn emit a photon (light). Different atoms release light in different colours, the greenish colour seen here is emitted by oxygen atoms.
Doug Wheelock has some out of this world pictures on Twitpic page, check it out!