Lightning is a familiar sight throughout the solar system. Not only do bolts strike on Earth, but they also sizzle through the air on Venus, Mars, Jupiter, Saturn, Uranus, and (most likely) Neptune. But lightning isn’t the only electrical phenomenon that can occur in a planet’s atmosphere. Stunning, evanescent events called sprites and elves are sometimes seen prancing above thunderclouds on Earth.
Now, NASA’s Juno spacecraft appears to have captured these
flashes in the stormy clouds of Jupiter — marking the first time these events have been observed on another planet. The new research was published October 27 in the
Journal of Geophysical Research: Planets.
Atmospheric sprites and elves
Both sprites (which stands for — get ready for it —Stratospheric/mesospheric Perturbations Resulting from Intense Thunderstorm Electrification) and elves (Emission of Light and Very Low Frequency perturbations due to Electromagnetic Pulse Sources) are a type of
transient luminous event, or TLE. These strange phenomena, which only last milliseconds, are occasionally seen above thunderstorms.
And although sprites may be visible with sharp, dark-adapted eyes, both phenomena are more often caught on film. Sprites were serendipitously captured by a camera for the first time in 1989, but the existence of elves wasn’t confirmed until orbiting
space shuttles recorded them on video in the 1990s.
Sprites typically have a round, blobby center that sprouts tendrils of light reaching upward or downward. They can look like anything from trees and jellyfish to the fairy tale creatures for which they’re named. Sprites occur when lightning bolts funnel positive charge from cloud to ground, leaving the cloud negatively charged. This, in turn, triggers activity in the atmosphere above the storm: a sprite.
Unlike lightning, which heats the air to incredible temperatures, sprites aren’t hot. They’re actually a cold plasma (think fluorescent light), not a bolt of electricity. They originate at altitudes around 40 miles (65 kilometers) high, but their wispy filaments can reach down as low as 20 miles (30 km) above the ground.
Elves, on the other hand, look more like expanding doughnuts or rings. They occur higher than sprites, around 62 miles (100 km) above the ground, reaching diameters up to 300 miles (480 km) wide. But even though elves are often spotted alongside sprites, the two aren’t caused by the same effect. Instead, elves form when electromagnetic pulses released during a thunderstorm slam into the ionosphere.