Earth’s magnetic field can capture the magnetic field associated with a large explosion, producing a coherent oscillating electric current.
An electromagnetic pulse (EMP) is a quick and powerful burst of electromagnetic energy that covers a significant part of the electromagnetic spectrum. The most cited source of an EMP is a nuclear weapon. In fact, the easiest way to generate energy for an EMP is through an abrupt chemical or nuclear explosion, and devices for creating PEM in the absence of such an explosion are known to be relatively weak.
The easiest way to generate power for a PGA is through an abrupt chemical or nuclear explosion.
The general idea of an EMP is that it wreaks havoc on electronics but leaves other physical structures largely untouched. Real-life electromagnetic pulses released by high-altitude nuclear tests have fused power wires, set off burglar alarms and caused radios, TVs and power lines to break up to 1,500 kilometers (930 miles) away. The source of this disruption is a large-scale, wildly fluctuating magnetic field created when high-energy photons from an explosion knock electrons out of their atomic orbits. This interruption gets trapped in the Earth’s magnetic field, leading to a coherent, oscillating electrical current.
An electromagnetic pulse is a burst of electromagnetic energy that spans the entire electromagnetic spectrum.
In near-future science fiction, the EMP is seen as a potent superweapon that disables all sophisticated electronics in a national or even continental region. Since the EMP can extend to the horizon with enough energy, a nuclear weapon detonated in near-Earth orbit could indeed disrupt electronics over a large region. In contrast, a nuclear weapon detonated close to the ground can do little damage with its EMP – for example, planes that drop atomic weapons continue to function even if they are within sight of the nuclear explosion.
To release an EMP capable of causing damage over a wide area, the nuclear weapon that triggers it must be relatively large – in the range of 10 megatons or more, which is nearly three orders of magnitude more powerful than the nuclear bombs dropped on Hiroshima and Nagasaki. . To release a powerful EMP over a smaller area, the explosively pumped flow compression generator has been suggested, which uses high explosive to essentially achieve the same effect. The military of the world tested prototypes of such a weapon, but it was not widely used.
The EMP is presented in fiction or games as a weapon suitable for use against machines, cyborgs or nanobots, but useless against biological creatures. In reality, machines can easily use processing and drive elements based on mechanical and chemical principles rather than purely electrical ones, making them as immune as a human being to an electromagnetic pulse.