Iceland's Volcanic Ash Against The Northern Lights.

I absolutely love this photograph owned by Reuters of thick black smoke rising above Eyjafjallajokull against the beautiful natural phenomenon known as the Northern Lights. These green auroras are caused by the emissions of photons in the Earth's upper atmosphere, above 80 km (50 miles), from ionized nitrogen atoms regaining an electron, and oxygen and nitrogen atoms returning from an excited state to ground state. They are ionized or excited by the collision of solar wind particles being funneled down and accelerated along the Earth's magnetic field lines; excitation energy is lost by the emission of a photon of light, or by collision with another atom or molecule.

Enough of geeky information. Enjoy the photograph.