14 DAY TRIAL // Sprites are not only legendary elf-like creatures, like fairies, dwarves and spirits from the European folklore. They are also electrical discharges that occur high above the cumulonimbus cloud of an active thunderstorm.
The mythical creatures gave their names to quick bursts of electricity that puzzled scientists for many years, since they couldn't explain their formation mechanisms, high above the trailing stratoform regions of active thunderstorm systems.
Sprite lightnings appear as luminous reddish-orange, plasma-like flashes, that last longer than normal lower stratospheric discharges (typically around a few milliseconds) and are thought to be triggered by the transient electric fields associated with discharges of positive lightning between the cloud and the ground and are generally delayed behind the stroke by a few milliseconds.
Sometimes appearing as far as 50 km (30 miles) away from the original lightnings, they have proven to be extremely difficult to capture on camera, since the first direct evidence was observed in 1989, almost 70 years after the first prediction of their existence.
Now, a team of scientists produced a new, ultra-high-speed video, that shows sprites forming as fast-paced balls of electricity, instead of the streaks or tendrils previously suggested, challenging current theories of how the mysterious sprites form.
"When the lightning strikes, an imbalance of charge forms between the storm cloud and the air above it," said Hans Nielsen, an atmospheric physicist at the University of Alaska and co-author of the new study. "Nature's way of evening things out is a rapid discharge of electricity-a sprite-that can extend as much as 20 miles upward. In the night sky, sprites can briefly outshine all other objects. You could, theoretically, see them in daylight," Nielsen said.
In the mountains of New Mexico, they found intriguing lightning patterns and models. "We now see them as compact balls of light, shooting downwards, then upwards, at one tenth the speed of light," said Nielsen. "Slower cameras can't show this. All you see are streaks or tendrils or blurred versions of the balls."
According to their estimations, each "sprite" occupies the space of a football field in the sky.
