Electromagnetic pulses from nuclear explosions

Apart from their many other effects, detonated nuclear explosives become coupled to electromagnetic fields and send out electromagnetic pulses (EMPs). To the author´s knowledge, the first observation of this effect was on 16 July 1945, by Enrico Fermi at the experimental Trinity explosion. The expanding ionized gases in the fireball displaced the earth´s magnetic fields and in this way created electromagnetic radiation. It is now known that EMPs of at least several tens of kilovolts per meter might be generated over wide areas from high-altitude nuclear explosions. Similar and even stronger internally generated EMPs have to be considered in spacecraft. The immediate result is that the electronic memory of an exposed system might be erased. If sufficient energy is concentrated on a semiconductor or on its electrical connections, some of this vital equipment may be permanently wiped out. Today there is almost universal dependence on electronic computers. They are used by first-graders as well as by research engineers. Industry, communications, financial records - all are at stake here. In the event of heavy EMP radiation, I suspect it would be easier to enumerate the apparatus that would continue to function than the apparatus that would stop. In almost all cases, adequate protection can be provided in theory. However, this would entail considerable expense. A final point must be stressed: what is involved in a consideration of EMP is knowledge that, to a great extent, is classified today. The military establishment can take the measures needed for defense because it possesses the classified information. But without widespread dissemination of information to industry - and therefore without actual declassification of essential parts of the EMP discussion - the civilian economy faces the prospects of grinding to a halt in a nuclear encounter.