EMP is shorthand for electromagnetic pulse. It is a rather unusual and frightening by-product caused by a nuclear bomb detonation above the earth’s atmosphere. We all know that our atmosphere and the magnetic field that surrounds our planet is a thin layer that not only keeps us alive, but also protects us from dangerous radiation from the sun. On a fairly regular basis there are huge solar storms on the sun’s surface, which emit powerful jets of deadly radiation. If not for the protective layer of our atmosphere and magnetic field, those storms would fry us. At times though, a storm is so powerful that enough disruptive energy reaches the earth’s surface to drown out radio waves and even short electrical power grids. This happened several years back in Canada.
The detonation of a nuclear bomb, two hundred miles straight up is almost the same thing as a solar storm, but infinitely more powerful since it is so close by.
As the bomb explodes it emits a powerful wave of gamma rays. As this energy release hits the upper atmosphere it creates an electrical disturbance known as the Compton Effect. The intensity is magnified, like a small pebble rolling down a slope, hitting a larger one, and setting that one in motion until finally you have an avalanche.
At the speed of light this disturbance races to the earth surface. It is not something you can see or hear; in the same way you don’t feel the electrical disturbance in the atmosphere during a large solar storm.
For all electrical systems though, it is deadly.
Those who remember ham radio operators, or even the old CB radios of the 1970s, can recall that if you ran out a wire as an antenna you could send and receive a better signal. The wire was capable of not only transmitting signals from your radio with very little power, but receiving even faint signals in return as well. As an electromagnetic pulse strikes the earth’s surface, with a power that could reach up to hundreds of volts per square yard, it will not affect you directly. At most you’ll feel a slight tingling, the same as when lightning is about to strike close by, and nearly all the energy will be absorbed into the ground and dissipate. The bad news, however, is wherever it strikes wires, metal surfaces, antennas, or power lines it will travel along those metal surfaces (in the same way lightning will always follow the metal of a lightning rod, or the power line into your house). The longer the wire, the more energy is absorbed. A high tension wire miles long will absorb tens of thousands of volts, causing destruction as the energy slams into any delicate electronic circuits meaning computer chips, relays, and so on. In that instant, the circuits will be overloaded by the massive energy surge, causing them to short circuit and fry. The energy surge will destroy all delicate electronics in your home, even as it destroys all the major components in the power company’s generators and the phone company’s main relays. In far less than a millisecond the entire power grid of the United States, and all that it supports, will be destroyed.
As of today, at least in the civilian sector, next to nothing has been done to “harden” our national infrastructure against such an event, be it from a military strike using one to three small nuclear weapons detonated above the continental United States, or from a major solar flare. Former Congressman Roscoe Bartlett, who for more than a decade was the leading voice on the floor of Congress regarding this issue, called for preparedness and infrastructure upgrades and explained why nothing has been done, saying that, “Until there is a national constituency of citizens demanding action, EMP will continue to be a ‘non-issue’ while far less important causes hold center stage and media attention.”