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The Beirut port explosion on August 4, 2020 was one of the largest non-nuclear explosions on record, leaving hundreds dead and thousands injured. Sensors as far away as Tunisia and Germany recorded the deep boom, and 500 kilometers away seismic stations recorded the tremor.
Today it appears that the blast shook the upper atmosphere and research data on the blast could benefit future efforts to monitor weapons tests.
Researchers from the National Institute of Technology in India, Rourkela, and the University of Hokkaido in Japan measured electrical disturbances in the ionosphere and found that the effect of the Beirut explosion was similar to that of many volcanic eruptions.
“We found that the explosion led to the creation of a wave that moved through the ionosphere in a southward direction, at a speed of about 0.8 kilometers per second,” says Kosuke Heikki, a planetary and terrestrial scientist at the University of Hokkaido.
The ionosphere begins about 50 kilometers above the Earth’s surface and extends into space hundreds of kilometers. It is characterized by a large number of free electrons that are released from gas molecules by solar radiation.
On the day of the Beirut explosion, the team used to measure phase differences within microwave transmissions sent by the Global Navigation Satellite System (GNSS) to calculate changes in electron distribution, which in turn indicate the presence of sound waves through gases. .
This is a trick that scientists have used since the advent of satellite networks in the 1990s, to measure the waves that spread through the upper reaches of our atmosphere, to notice subtle signals from anything from volcanoes to tests. dishonest nuclear weapons.
One of the first experiments to use global positioning satellite (GPS) technology to measure explosions at the surface occurred in the mid-1990s, when scientists harnessed three huge underground explosions at a coal mine in Wyoming, United States, to study how the ionosphere responds. .
Finding the fading traces of the Beirut explosion in this case was not without a bit of luck. Irregularities in the ionosphere, called equatorial plasma bubbles, may have completely obscured the signal by bubbling the event in the early evening and near dusk.
Fortunately, there were no signs of these bubbles at the time, giving scientists a relatively clear picture of the eruption gliding through the atmosphere above the speed of sound.
The researchers compared the effect of the Beirut explosion on the ionosphere with similar scars from several recent volcanic eruptions in Japan, and found that they are somewhat comparable. In the case of the 2004 eruption of the “Asama” volcano in central Japan, the Beirut eruption is much more effective.
Although slightly weaker than the 1.5 kiloton blasts, which have been studied in recent decades at the Wyoming mine, the fact that this blast occurred on the Earth’s surface gave it an unobstructed path to the sky. , with an energy release evident in the data. .
Building a database of acoustic effects that GNSS can detect provides scientists and authorities with a way to monitor the geological dynamics of our world.
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