An EMP is an intense, broadband burst of electromagnetic energy. It can be the result of many things, including lightning, a nuclear explosion, or specialized weapons. Each is briefly discussed below.
Lightning—Many people are familiar with the “buzz” or “pop” that can be heard in electronic systems when a nearby lightning strike occurs. Most of the time, the resultant electromagnetic wave is not sufficiently strong enough to cause permanent damage but might instead reset computers or cause some other noticeable (but temporary) malfunction.
Nuclear Explosion—Electromagnetic waves are generated as a byproduct of a nuclear explosion. If the detonation is high in the atmosphere, the waves can propagate down to the surface and damage electronic hardware across a very large area. A high-altitude nuclear EMP attack is viewed as a serious national threat and is, therefore, the main focus of this chapter.
Specialized EMP Weapons—Military weapons have been created with the sole purpose of generating disruptive EMPs. Some are directed-energy weapons that use high-powered microwaves (HPM) to emit high-frequency electromagnetic energy. Others are E-bombs built around conventional explosives teamed with pre-charged electronic circuits. Two widely cited EMP weapons are the explosively pumped coaxial flux compression generator (FCG) and the virtual cathode oscillator vircator). Weapons of this type are typically used for disrupting electronics in localized areas, such as across a military compound.
Of these three sources, the EMP that results from a nuclear explosion has the greatest potential to cause widespread damage to our country. When people discuss an “EMP attack,” they are almost always referring to one that is a result of a high-altitude nuclear detonation.