12 December 2013
Amid flashing lightning and booming thunder, storms emit a very powerful but little understood form of energy — gamma radiation.
These terrestrial gamma-ray flashes (TGFs) produce short-lived but immensely powerful bursts of energy that could zap airplane passengers with unhealthy doses of radiation. Now, researchers at the University of California, Santa Cruz think they might be able to use a smartphone app to learn more about these mysterious bursts.
Scientists are still deciphering TGFs. The flashes were discovered in 1991 when a spacecraft searching for extraterrestrial radiation spotted energy coming from the wrong direction: the Earth. They’ve only been detected two times from the ground, in part because the atmosphere skews measurements, according to physicist Joseph Dwyer, who studies TGFs at Florida Institute of Technology.
“We’ve got these things right above our heads that we can’t examine,” Dwyer said Tuesday at the American Geophysical Union’s Fall Meeting in San Francisco.
Scientists need more measurements to figure out several remaining puzzles, according to UC Santa Cruz graduate student Gregory Bowers. For example, no one knows how many TGFs a thunderstorm produces or how they are generated, he said.
Researchers are exploring different ways to examine the bursts. Dwyer is refining methods to track TGFs using radio waves and NASA operates a radiation tracker known as ADELE (Airborne Detection for Energetic Lightning Emissions), which identified one burst in 2009.
But it might just be easier to use cell phones. Working with a team, Bowers plans to search for TGFs using GammaPix, an app designed to test for radiation from medical devices, power plants or other environmental sources. The app’s developer, astrophysicist Eric P. Rubenstein of Image Insight, thought the app could recognize TGFs and asked the UC Santa Cruz team to try it out, Bowers said.
GammaPix accurately detects radioactive cesium and stood up to a modal-based test of its ability to spot a TGF, Bowers said.
To search for gamma rays, app users must place a sticker or other light blocker across the phone’s image scanner — the tiny lens that measures mere microns in diameter. With no light striking the scanner, any incoming electrons must stem from radiation, Bowers said.
He plans to mount a retrofitted smartphone in a weather balloon to launch into storm centers. The app could also be useful if it is downloaded by many frequent flyers, allowing those most at risk for exposure to help study the emissions, Bowers said.
– Becky Bach is a science communication graduate student at UC Santa Cruz