From NASA Goddard Space Flight Center. NASA’s The Fermi Gamma-ray Space Telescope has been catching brief outbursts of high-energy light that are mysteriously produced above thunderstorms. The outbursts, known as terrestrial gamma-ray flashes (TGFs), last only a few thousandths of a second, but their gamma rays rank among the highest-energy light that naturally occurs on Earth. The enhanced GBM discovery rate helped scientists show most TGFs also generate a strong burst of radio waves, a finding that will change how scientists study this poorly understood phenomenon.
Lightning emits a broad range of very low frequency (VLF) radio waves, often heard as pop-and-crackle static when listening to AM radio. World Wide Lightning Location Network (WWLLN) researchers routinely detect these radio signals and use them to pinpoint the location of lightning discharges anywhere on the globe to within about 20 km. Scientists have known for a long time TGFs were linked to strong VLF bursts, but they interpreted these signals as originating from lightning strokes somehow associated with the gamma-ray emission.
The researchers identified much weaker radio bursts that occur up to several thousandths of a second before or after a TGF. They interpret these signals as intracloud lightning strokes related to, but not created by, the gamma-ray flash. Scientists suspect TGFs arise from the strong electric fields near the tops of thunderstorms. Under certain conditions, the field becomes strong enough that it drives a high-speed upward avalanche of electrons, which give off gamma rays when they are deflected by air molecules. Because the WWLLN radio positions are far more precise than those based on Fermi’s orbit, scientists will develop a much clearer picture of where TGFs occur and perhaps which types of thunderstorms tend to produce them.
The GBM scientists predict the new operating mode and analysis techniques will allow them to catch about 850 TGFs each year. While this is a great improvement, it remains a small fraction of the roughly 1,100 TGFs that fire up each day somewhere on Earth, according to the team’s latest estimates.
If you value what we do here, open your ad-free account and support our journalism.
Producing content you read on this website takes a lot of time, effort, and hard work. If you value what we do here, select the level of your support and register your account.
Your support makes this project fully self-sustainable and keeps us independent and focused on the content we love to create and share.
All our supporters can browse the website without ads, allowing much faster speeds and a clean interface. Your comments will be instantly approved and you’ll have a direct line of communication with us from within your account dashboard. You can suggest new features and apps and you’ll be able to use them before they go live.
You can choose the level of your support.
Stay kind, vigilant and ready!