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A Royal Air Force bomber making an attack on a German synthetic oil plant in 1944 during World War II.

Many Allied bombings released the equivalent energy of 300 lightning strikes and temporarily weakened the ionosphere, say researchers.

During World War II, Allied bombing raids left their devastating mark on Germany, killing more than 400,000 civilians and laying waste to entire cities, from Berlin to Hamburg to Dresden.

The bombings were so intense that, according to new research, they sent shockwaves all the way to the edge of space and briefly weakened the outermost layer of Earth’s atmosphere, known as the ionosphere.

By studying daily records at the Radio Research Center in Slough, in the United Kingdom, a team of researchers tracked how the concentration of electrons in the ionosphere changed around the time of 152 Allied air raids in Europe. These included major bombing raids of German cities between 1943-45, as well as those bombs dropped in support of the major Allied landing at Normandy that began on D-Day, June 6, 1944.

During the conflict, Royal Air Force (RAF) and other Allied planes could carry much more weight than their counterparts in the German Luftwaffe. This allowed them to deploy such monster bombs as the “Grand Slam,” which weighed in at some 22,000 pounds and left a crater some 70 feet deep and 130 feet around during a top-secret test in March 1945.

Imperial War Museum/Public Domain
The British Grand Slam bomb.

The researchers who conducted the new study found that when Allied bombs hit the ground, the shockwaves reached as far as 1,000 kilometers (or 621 miles) into the air. This heated up the upper atmosphere and caused the concentration of electrons in it to drop, resulting in a temporary weakness in the ionosphere.

According to their findings, published in the European Geosciences Union journal Annales Geophysicae, each bombing raid released the energy of 300 lightning strikes. Evidence showed that even though the bombs exploded in Germany, the changes could be seen in the ionosphere above Slough, hundreds of miles away.

“These were very temporary effects which heated the atmosphere very slightly,” the new study’s co-author, Chris Scott, a space and atmospheric physicist from the University of Reading (U.K.), told BBC News. "The effects on the ionosphere would only have lasted until the heat dissipated."

Temporary or not, these findings have implications for understanding the impact of other, natural events on the ionosphere, such as volcanic eruptions, earthquakes and thunderstorms.

“Because we know the energies involved in these explosions, that gives us a real quantifiable way of assessing how much energy is required to make the ionosphere warmer,” Scott told CNN.

Research into how the volatile particles that make up the ionosphere react to such events is critical, as many modern technologies—including radio communications systems and GPS—can be affected when the ionosphere is disturbed. NASA is already studying the ionosphere as part of its ICON and GOLD missions, both launched in 2018