Even underground nuclear tests leave their mark on the part of the upper atmosphere known as the ionosphere, the researchers discovered, when they examined GPS data recorded the same day as a North Korean nuclear test in 2009. Within minutes on that day, 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.
“Its 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 author on the study.
Jihye Park, a doctoral student in geodetic science at the university, is presenting the results of the study this Wednesday, Thursday, and Friday in a poster session at the CTBTO meeting in Vienna, Austria.
International authorities already possess several methods for detecting illegal nuclear tests, Park said. Seismic detectors pick up shockwaves through land, and acoustic sensors monitor for shockwaves through water and the air for tests that happen above ground. 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,” she 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.
“GPS signals must pass from transmitters on satellites high above the planet down to ground-based receivers,” Grejner-Brzezinska explained. “Air molecules – more specifically, the electrons and other charged particles in the ionosphere – interfere with the signal, generating position error. Part of our research concerns how to compensate for that vulnerability and make GPS work better. Jihye found a way to take that vulnerability and turn it into something useful.”Park wrote computer algorithms that search GPS signals for patterns indicating a sudden fluctuation in atmospheric electron density in specific locations, which is what happens when a shockwave pushes a bubble of air through the atmosphere. As the GPS signal passes through the edge of the bubble, the change in electron density disturbs the signal in a noticeable way.
When Park analyzed the data from the 11 GPS stations, she detected a sudden spike in atmospheric electron density after the May 25, 2009 underground test, which is believed to have happened just before 1:00 a.m. Coordinated Universal Time that day.
Within 25 minutes, the shockwave had traveled 225 miles to the nearest GPS station in the study, which was located in Inje County, in Gangwon Province, South Korea. That means that it was traveling through the air at 9 miles per minute, or 540 miles per hour. Within that first hour, it had reached all 11 stations.
Based on the timing of the shockwave, the researchers traced the origin of the explosion back to P’unggye, in Hamyong Province, North Korea. This finding agrees with seismic data from the event, which was collected by the CTBTO and the US Geological Survey.
The researchers will continue this work as Park earns her PhD, and they are seeking funding and partnerships to expand it further. In the meantime, they have submitted a paper on the discovery to the journal Geophysical Research Letters.
Collaborators on the study include Yu Morton, professor of electrical and computer engineering at Miami University in Oxford, Ohio, and Luis Gaya-Pique of CTBTO’s On-Site Inspection Division.Ralph von Frese, (614) 292-5635; Vonemail@example.com
Ralph von Frese | EurekAlert!
Drones learn to navigate autonomously by imitating cars and bicycles
23.01.2018 | Universität Zürich
Cloud technology: Dynamic certificates make cloud service providers more secure
15.01.2018 | Technische Universität München
Physicists have developed a technique based on optical microscopy that can be used to create images of atoms on the nanoscale. In particular, the new method allows the imaging of quantum dots in a semiconductor chip. Together with colleagues from the University of Bochum, scientists from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute reported the findings in the journal Nature Photonics.
Microscopes allow us to see structures that are otherwise invisible to the human eye. However, conventional optical microscopes cannot be used to image...
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
24.01.2018 | Physics and Astronomy
24.01.2018 | Health and Medicine
24.01.2018 | Health and Medicine