Scientists have developed a radar, located at an altitude of 100 km, capable of detecting small nuclear explosions and warning of impending earthquakes and tsunamis. It takes advantage of the fact that the upper atmosphere is ionized to detect disturbances at the Earth’s surface.
Scientists have detected a domino effect of small explosions in the ionized layers of the upper atmosphere up to 100 kilometers high at ground level.
This result suggests that this remote sensing technique could be used to monitor explosive events, natural or man-made, hundreds of times smaller than previously thought, reports the journal Science.
The ionized region of the atmosphere, or ionosphere, is the layer of Earth’s atmosphere that extends between an altitude of about 80 to 500 km. There are abundant ionization processes in it, in which large concentrations of free electrons are generated.
Sensitive ionosphere
The ionosphere is most famous for being home to the auroras, which occur when charged particles from the Sun collide with atoms, setting them on fire.
But massive explosions that erupt from below can disturb the ionosphere as well. In 2022, the Hanga Tonga-Hanga Ha’apai volcanic eruption in the South Pacific Ocean produced ripples in the ionosphere that were detected thousands of kilometers away.
In 1979, the now defunct Arecibo Radio Telescope in Puerto Rico detected an ionospheric disturbance associated with an alleged Israeli-South African nuclear test.
Both explosions spread infrasound waves, too low a pitch for human hearing, which can propagate over great distances and cause vibrations even in the ionosphere.
Those vibrations can be picked up by radar tuned to bounce off charged particles in the ionosphere. These radars take advantage of the fact that the upper atmosphere is ionized and therefore a good target for radar.
New radar
In the past this technology has been limited to detecting explosions more powerful than 1 kiloton of TNT. However, the authors of the new research, whose results are published in the journal Earth and Space Sciences, present a different method for detecting small disturbances in the ionosphere that had not been previously recorded: they used this new technique to obtain similar performance. Used to detect explosions. 1 ton of TNT, the researchers write in their article.
Kenneth Oberenberger, a physicist at the Air Force Research Laboratory and director of the study, explained that with this technique they were able to observe the effects of two 1-ton explosions that occurred in March 2022 in New Mexico, a novelty in the field. Investigation.
The detectors of this new radar were designed to measure waves that bounce off the E layer of the ionosphere, a region located at an altitude of about 100–140 km, which varies with the seasons of the year. And they worked: They detected signals from each explosion less than 6 minutes after the explosion.
Tsunami warning
Obenberger, quoted by Science, says the technique could be used to monitor small human-caused eruptions or remote volcanic eruptions in the Pacific that would otherwise be difficult to detect.
The improved resolution provided by this technology will make it easier to detect not only ionospheric disturbances associated with volcanic eruptions, but also earthquakes, which can trigger tsunamis, landslides and other disasters.
This means that this technique can be used for early warning systems, such as tsunami warning systems.
Another possible use could be in planetary science. For a world like Venus, where thick clouds obscure the surface, ionospheric radar on orbiting spacecraft could detect invisible explosions and earthquakes from afar, says Oberenberger.
