Impact of WWII bombing felt at the edge of space

Study shows the ionosphere was affected by the sheer power of Allied bombing across Europe. Nick Carne reports.

Lancaster bombers starting out on an Allied bombing raid in World War II.

Lancaster bombers starting out on an Allied bombing raid in World War II.

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Allied bombing in Europe during World War II sent shockwaves through the Earth’s atmosphere that were detected at the edge of space, a new study has found.

Researchers from the University of Reading in the UK estimate that each of the more than 150 raids released the energy of at least 300 lightning strikes and say the impact significantly decreased the electron concentration in the upper atmosphere.

This is thought to have heated the upper atmosphere, enhancing the loss of ionisation.

“The sheer power involved has allowed us to quantify how events on the Earth’s surface can also affect the ionosphere,” says meteorologist and co-author Chris Scott.

The ionosphere is important to modern technologies such as radio communications, GPS systems, radio telescopes and some early-warning radar. It is unclear to what extent radio communications during the war were affected.

In their study, which is published in the journal Annales Geophysicae, Scott and colleagues examined daily records collected from between 1943 and 1945 at the Radio Research Centre in Slough, just west of London.

Sequences of radio pulses over a range of shortwave frequencies were sent 100 to 300 kilometres above the Earth’s surface to reveal the height and electron concentration of ionisation within the upper atmosphere.

The strength of the ionosphere is known to be strongly influenced by solar activity, but is also far more variable than can be explained by current modelling.

Although the London Blitz bombings were much closer to Slough than those in Europe, their continuous nature and a lack of surviving information has made it difficult to assess their impact.

However, there are detailed records of the Allied raids and these reveal that the four-engine planes routinely carried much larger bombs than the German Luftwaffe’s two-engine ones could.

Historian and co-author Patrick Major says the crew involved in the raids reported having their aircraft damaged by the 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,” he says.

“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.”

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