Mysterious Dark Lightning Detected by Satellites: Burst of Radiation Linked to Storms

Dark lightning could be affecting airline passengers and pilots, but researchers know very little about the intense burst of radiation. Now, they could have discovered a little bit more about the phenomenon; researchers have identified a burst of dark lightning immediately preceding a flash of ordinary lightning. The observational evidence could show that the two phenomena are connected.

Dark lightning is a burst of gamma rays produced during thunderstorms by extremely fast moving electrons that collide with air molecules. It's actually the most energetic radiation produced naturally on Earth, but was undiscovered before 1991. The powerful bursts of gamma rays from dark lightning possess the ability to blind sensors on satellites hundreds of miles away, according to Discovery News. Yet while they're bright to the satellites, they're barely noticeable to humans. It's unlikely that many people flying have even noticed the faintly purple flashes.

Yet while people may not notice this dark lightning, they may be affected by it while flying. At the top of thunderstorms at about 40,000 feet, radiation doses are comparable to about 10 X-rays, or the same dose that people receive from natural background sources of radiation over the course of an entire year. In the middle of the storms at about 16,000 feet, radiation doses could be about 10 times larger and comparable to some of the largest doses received during medical procedures--such as a full-body CT scan.

This, in part, is what has prompted the recent research into how dark lightning is formed. In 2006, two independent satellites--one equipped with an optical detector and one carrying a gamma ray detector--flew within 186 miles of a storm over Venezuela just as a powerful lightning bolt exploded within a thundercloud. Now, researchers have examined the data that these satellites collected and have discovered evidence of a weak flash of dark lightning that preceded the lightning bolt.

"This observation was really lucky," said Nikolai Østgaard, one of the researchers, in a news release. "It was fortuitous that two independent satellites, which are traveling at 7 kilometers per second (4.3 miles per second), passed right above the same thunderstorm right as the pulse occurred.

The findings could allow researchers to understand a little bit more about dark lightning. In particular, it reveals that regular lightning is connected to the gamma radiation, though researchers need to conduct more studies to see exactly how the two are linked. Currently, the European Space Agency is planning on launching the Atmospheric Space Interactions Monitor (ASIM) within the next three years. This will be able to better detect both dark and visible lightning from space, and could lead to future discoveries.

The findings are published in the journal Geophysical Research Letters.

Want to learn more about dark lightning? Check out the video below, courtesy of the American Geophysical Union.