Shockwaves from dropping bombs in the middle of a war can be felt for miles, but researchers recently discovered those miles can extend far into space.
Researchers with the University of Reading discovered just how far bombing raids traveled; they uncovered shockwaves produced by the biggest bombs that managed to weaken the ionosphere.
Their findings were published in the European Geosciences Union journal Annales Geophysicae.
Studying an era of war
During World War II, both Allied and German forces conducted extensive bombing raids. As the researchers pointed out, plenty of historical documentation exists detailing how that bombing affected structures, civilians, topography, and policies.
But until this point, an extensive look into how it affected Earth’s atmosphere -- particularly the upper layers -- hadn’t been investigated.
Chris Scott, Professor of Space and Atmospheric Physics, said: "The images of neighborhoods across Europe reduced to rubble due to wartime air raids are a lasting reminder of the destruction that can be caused by man-made explosions. But the impact of these bombs way up in the Earth's atmosphere has never been realized until now."
The researchers used at daily records at the Radio Research Center in Slough, UK collected during the peak years of the bombing: 1943-45. They looked at sequences of radio pulses over shortwave frequencies sent 100-300 km above Earth’s surface to look at the electron concentration of ionization within the upper atmosphere.
While much of the ionosphere is affected by solar activity, it still can vary given other forces. The ionosphere also has an impact on modern communication technologies like radio, GPS, radio telescopes, and early warning radar.
“Researchers studied the ionosphere response records around the time of 152 large Allied air raids in Europe and found the electron concentration significantly decreased due to the shockwaves caused by the bombs detonating near the Earth's surface,” the researchers explained. “This is thought to have heated the upper atmosphere, enhancing the loss of ionisation.”The researchers also compared their data with records of the Allied forces raids.
They noted that four-engine planes often carried larger bombs than the German Luftwaffe’s two-engine planes could, most notably the 10-tonne Grand Slam.
"It is astonishing to see how the ripples caused by man-made explosions can affect the edge of space. Each raid released the energy of at least 300 lightning strikes. The sheer power involved has allowed us to quantify how events on the Earth's surface can also affect the ionosphere."
The researchers further explored the historical impact of these bomb deployments.
Professor Patrick Major, University of Reading historian and a co-author of the study, said: "Aircrew involved in the raids reported having their aircraft damaged by the bomb shockwaves, despite being above the recommended height. Residents under the bombs would routinely recall being thrown through the air by the pressure waves of air mines exploding, and window casements and doors would be blown off their hinges. There were even rumours that wrapping wet towels around the face might save those in shelters from having their lungs collapsed by blast waves, which would leave victims otherwise externally untouched."
Applying blast history to future events
The findings could contribute to a better understanding of how natural and man-made forces on the earth affect the upper atmosphere.
"The unprecedented power of these attacks has proved useful for scientists to gauge the impact such events can have hundreds of kilometers above the Earth, in addition to the devastation they caused on the ground," said Major.