Strokes of lightning flashing down towards the ground are a familiar sight during summer thunderstorms, but scientists have capture an image of a rare lightning bolt shooting out upwards from a cloud, almost to the edge of the Earth's atmosphere.
These bolts of upwards lightning, one type among a variety of electrical discharges now known to occur above thunderstaorms, are called gigantic jets, and were only first discovered in 2001.
Since then, only about 10 gigantic jets have been observed, said Steven Cummer, who was part of the team that photographed this most recent jet. Gigantic jets are essentially the same as cloud-to-ground lightning, only they go the opposite way.
"Gigantic jets are literally lightning that comes out of the thunderclouds, but instead of going down, like most lightning strokes do, these apparently find their way out the tops of thunderclouds, and then keep going and keep going and keep going until they run into something that stops them," Cummer explained.
The something that stops them is the ionosphere, the topmost layer of the Earth's atmosphere (right at the edge of space), which is made up of electrically charged atoms, or ions.
The observations, detailed Sunday in the online issue of the journal Nature Geoscience, confirm that gigantic jets transfer charge from clouds to the highest layers of the Earth's atmosphere, just as their downwards cousins transfer it to the ground.