A nuclear electromagnetic pulse (NEMP) is a burst of electromagnetic radiation created by a nuclear explosion. The resulting electric and magnetic fields can cause current and voltage surges that can damage electrical and electronic systems. The characteristics of a nuclear EMP event depend on the altitude of the detonation. If the symmetry of the ionized sphere is altered, non-radial oscillations will begin and energy will be emitted in the form of a pulse of electromagnetic radiation, much of which is in the radio frequency region of the spectrum.
The high-altitude nuclear tests of Bluegill Triple Prime and Kingfish provided data that allowed physicists to identify the physical mechanisms behind electromagnetic pulses. During the first nuclear test in the United States, Enrico Fermi was waiting for the electromagnetic pulse. In July, Chinese researchers urged their government to increase their readiness to defend against a high-altitude EMP attack. The EMP Commission sponsored a global survey to assess foreign states' knowledge and intentions regarding EMP attacks.
The time-varying current produces an emission of a short pulse of electromagnetic radiation that is more intense in directions perpendicular to the current; this is the EMP. The effects of an EMP in outer space on the electrical grid are largely determined by the three-dimensional distribution of rocks under our feet. Components listed in Table 11.31 are listed in order of decreasing sensitivity to damage caused by an acute pulse of electromagnetic energy. Even a low-energy pulse has access to the power supply, and the pulse illuminates all parts of the system.
Whether caused by man or nature, episodes of electromagnetic pulses (EMP) and geomagnetic disturbances (GMD) have the potential to permanently interrupt and damage electrical components and entire systems in most critical infrastructure sectors. In military terminology, a nuclear warhead that detonates tens or hundreds of miles above the Earth's surface is known as a high-altitude electromagnetic pulse device (HEMP). It was already known in the early days of nuclear weapons testing that a nuclear explosion produces an EMP. Components that are known to be susceptible to damage due to sudden pulses of electromagnetic energy should be eliminated.
The two main types of large simulators are metal structures that guide an electromagnetic wave past a test object and antennas that radiate an electromagnetic field to the object. This interaction of negatively charged electrons with the magnetic field radiates a pulse of electromagnetic energy. As the gamma pulse traveling outwards propagates at the speed of light, the synchrotron radiation from the Compton electrons adds up in a coherent way, producing a radiated electromagnetic signal.