The bombs that the Allies threw on Germany during World War II were noticed even at the lower edge of space: the ionosphere weakened under the influence of the blast wave of so much explosive. Although the effect was temporary, it was felt on the skies of England. However, the German bombings, first of the Luftwaffe and then with the rockets V1 and V2 barely left a trace in the atmosphere.
From the 20s of the last century, the British Government had installed its Radio Research Center (RRC) in the town of Slough, twenty miles west of London. There, among many other investigations on the new technology, pulses of radio were emitted at different frequencies towards the sky that bounced against the charged particles of the ionosphere. This phenomenon, essential for radio transmissions, would help to better understand this outer layer of the atmosphere. The records began in 1933 and continue since then.
Located between the 80 kilometers (km) and the 600 km (very variable limits) of height, the ionosphere is formed by electrically charged particles due to solar radiation. The high temperatures recorded there, which can reach 1,500 degrees, have also reserved the name of thermosphere. Occasionally, this protective mantle of extreme radiations is disturbed from outside by winds or solar flares. On the bottom, only large earthquakes or storms with many rays can have a local impact on the ionosphere. But humans are also capable of upsetting the sky.
British researchers searched Slough’s records for the signals returned from the ionosphere, which are recorded constantly, and displayed the days and hours in which Germany (and French, Dutch and Belgian cities under German control) suffered massive bombardments by the allied forces. They only took into account the 152 most destructive, measured by the amount of explosives discharged, such as that which yielded 6,800 tons of TNT and derivatives on Caen, in French Normandy, in July 1944, which destroyed 98% of the city Jülich , with 9,600 tons in November of that year or the most intense of the many suffered by Berlin, with almost 11,000 tons of bombs in less than two hours, on January 29, 1944.