Lightning flashes occur 4.3 million times a day on Earth. The Firestation, a new instrument aboard the International Space Station, includes photometers to measure lightning flashes, radio antennas to measure the static (a proxy for the strength of the electrical discharge) and a gamma-ray electron detector.
Gamma radiation usually is associated with exploding stars or nuclear fusion, but scientists have found evidence that terrestrial gamma-ray flashes (TGFs) may occur in the atmosphere as often as 500 times a day. Atmospheric scientists are interested in the processes that trigger lightning within thunderstorms and what kinds of lightning produce gamma rays. TGFs may also be related to the atmospheric phenomena known as red sprites, electrical discharges that extend upward from thunderstorms.
“The fact that TGFs exist at all is amazing,” said Doug Rowland, the principal investigator for Firestation and a space physicist at NASA’s Goddard Space Flight Center. “The electron and gamma-ray energies in TGFs are usually the domain of nuclear explosions, solar flares and supernovas. What a surprise to find them shooting out of the cold upper atmosphere of our own planet.”
Image courtesy of NASA.