Elves are bright flashes of light in the night sky resulting from lightning within thunderstorms.
The thin upper atmosphere gives off a brief glow as the electromagnetic pulse from a lightning bolt passes through on its way to outer space.
Elves are too fast to be seen with the naked eye, and typically last for around just one millisecond.
Elves often appear as a dim, flattened, expanding glows around 250 miles (402 km) in diameter.
They occur in the ionosphere 60 miles (97 km) above the ground over thunderstorms.
Their color was a puzzle for some time, but is now believed to be a red hue.
Elves were first recorded on another shuttle mission, this time recorded off French Guiana on October 7, 1990.
Elves is an acronym for Emissions of Light and Very Low Frequency Perturbations from Electromagnetic Pulse Sources.
This refers to the process by which the light is generated.