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When's there's a nuclear blast, how does it create the EMP?

When a nuclear blast occurs, a number of things happen at once. Many high-energy photons (x-rays and gamma rays) are produced. These photons collide with electrons in the bomb debris or the surrounding air and strip them from their nuclei. This causes a movement of the electrons away from the atomic nuclei. This separation of charges generates an electric field, and the motion of the charged particles (electrons) also induces a magnetic field. Magnetic and electric fields that change with time are all you need to generate electromagnetic radiation.

Because of the high energy of a nuclear explosion and the high temperature of the fireball, these electromagnetic pulses pack quite a whallop. The frequency of the radiation in an EMP is fairly low, just in the range that electronic devices are sensitive to. Susceptible electronic circuits act as receivers, and pick up damaging voltage and current surges. The electronic components overheat, and that's the end of the device.

Richard Barrans Jr., Ph.D.

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