Washington: US researchers are unveiling a new tool for detecting illegal nuclear explosions: the earth`s global positioning system (GPS).Even underground nuclear tests leave their mark on the ionosphere in the upper atmosphere, the researchers discovered, when they examined GPS data recorded the same day as a North Korean nuclear test in 2009.
Within minutes, GPS stations in nearby countries registered a change in ionospheric electron density, as a bubble of disturbed particles spread out from the test site and across the planet.
"It`s as if the shockwave from the underground explosion caused the earth to `punch up` into the atmosphere, creating another shockwave that pushed the air away from ground zero," said Ralph von Frese, professor of earth sciences at Ohio State University and senior study author.
International authorities already possess several methods for detecting illegal nuclear tests, said Jihye Park, doctoral student in geodetic science at Ohio.
Seismic detectors pick up shockwaves through land, and acoustic sensors monitor for shockwaves through water and the air for tests that happen above ground, according to an Ohio statement.
Chemical sensors detect airborne radioactive gas and dust as definitive evidence of a nuclear explosion. However, these particles may be lacking if the explosion is contained deeply below ground.
"GPS is a complement to these other methods, and can help confirm that a nuclear test has taken place - especially when the test was underground, so that its effect in the air is very subtle, and otherwise nearly impossible to detect," Park said.
While GPS was designed for location purposes, the technology has always been especially sensitive to atmospheric disturbances, said Dorota Grejner-Brzezinska, a professor of geodetic science at Ohio State and Park`s advisor.