Scientists have uncovered a new link to dark lightning, a phenomenon of powerful gamma-ray radiation bursts first discovered in 1991. Thunderstorms produce dark lighting, also known as terrestrial gamma-ray flashes, and satellite data has now linked it to visible lightning.
According to data obtained from two satellites, right before a bolt of lightning was observed across a thundercloud, a flash of dark lightning occurred. One satellite detected optics and the other detected gamma rays. A study published on April 15 in the journal Geophysical Research Letters details the satellite data caught back in 2006 during a Venezuelan storm. Prior to the study, scientists were not aware that a dark lightning flash occurred before the visible lightning.
"This observation was really lucky. 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," space scientist at the University of Bergen in Norway, Nikolai Østgaard said.
Using a new technique to analyze the satellite data, the scientists were able to detect the connection of dark lighting to visible lightning. The team identified over twice as many terrestrial gamma flashes that were first reported with the development of an improved algorithm.
"Our results indicate that both these phenomena, dark and bright lightning, are intrinsic processes in the discharge of lightning," Østgaard said.
Although the link between dark and visible light was uncovered, more research will help scientists to understand more. Researchers still don't know how frequently the flashes occur or how often.
"Dark lightning might be a natural process of lightning that we were completely unaware of before 1991. But it is right above our heads, which makes it very fascinating," Østgaard said.
Within the next three years, the European Space Agency plans to launch a new gamma-ray detector. The Atmospheric Space Interactions Monitor (ASIM) will be capable of better detecting dark and visible lightning from space. Østgaard is working closely with the ESA team that is developing the ASIM gamma-ray detector.
