- Scientists revealed that shockwaves generated by heavy bombs used in World War II were detected at the edge of the space.
- These shockwaves were powerful enough to reduce the electron concentration of ionization in the upper atmosphere.
Researchers are currently investigating how natural forces like stratospheric warming, tectonic activity, thunderstorms, space weather, and solar variability affect Earth’s ionosphere. Despite recent advances in technologies analyzing near-Earth space, detecting the individual contribution of each force remains challenging.
Along with natural forces, man-made explosions play a significant role in impacting Earth’s upper atmosphere. Recently, researchers at the University of Reading in the UK revealed that shockwaves generated by heavy bombs dropped on European cities were powerful enough to erode the ionosphere above the United Kingdom (at 1,000 kilometers altitude).
It’s surprising to see how man-made explosives can impact the edge of space. Each bombing raid produced an energy of more than 300 lightning strikes. Researchers have studied the contribution of ground-based disturbances to Earth’s upper atmosphere by measuring the response of the F2 layer of the ionosphere over Slough (a town in England). To measures such responses, they used data analysis technique called Superposed Epoch Analysis.
Ionosphere Response Records
Researchers gathered the daily records (of 1943-1945) from Radio Research Center. They sent a series of radio pulses at altitudes between 100 and 300 kilometers (above the surface of the Earth) to know the electron concentration of ionization in the upper atmosphere.
Although the characteristics of the ionosphere are extensively influenced by solar activities, modern technologies can’t accurately model all of them. We do know that technologies like GPS, radio telescopes and warning radar affect ionosphere, but the extent of the radio communication impact during World War II isn’t clear.
Researchers found that the electron concentration in ionosphere significantly reduced due to the shockwaves of 152 heavy bomb raids over Europe. This might have heated the upper atmosphere over there, increasing the depletion of ionization.
The continuous nature of such attacks during World War II and less availability of surviving data made it extremely difficult to separately determine the impact of these explosives from natural impacts.
The records show that 4-engine airplanes carried heavy bombs, including 10,000 kilograms earthquake bombs named Grand Slam. Some aircraft were damaged by shockwaves, despite flying above the suggested altitude.
12th Bombardment Group | Credit: United States Army Air Forces via National Archives
Although no minimal mass of explosives required to produce such a response was uncovered in this research, raids using more than 100 tons of high explosive were observed to reduce the electron concentration of upper atmosphere above Slough.
One metric ton of tri-nitro-toluene (TNT) carries 4.184×109 Joules of explosive energy, nearly the same energy as a big lightning stroke. Since lightning occurs in seasonal cycles, it’s possible that a similar process could be responsible for the observed seasonal anomaly in electronic concentrations of ionospheric F-region.
Investigating the response of the ionospheric E layer to man-made explosions would provide more data on mechanisms involved in this process. The authors now require earlier atmospheric information to better understand the impact of several hundreds of smaller explosions during the war, which will eventually help them identify the minimum amount of energy required to trigger a response within Earth’s upper atmosphere.