The detonation of a nuclear weapon at high altitude can generate an intense and instantaneous energy field known as an electromagnetic pulse (EMP). This pulse can remotely overload or disrupt many high-tech electrical systems and microcircuits, which are particularly vulnerable to voltage surges. In military terminology, this type of nuclear warhead is referred to 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. During the first nuclear test in the United States, on July 16, 1945, electronic equipment was safeguarded because Enrico Fermi was expecting the electromagnetic pulse.
The EMP Commission sponsored a global survey of foreign scientific and military literature to evaluate the knowledge, and possibly the intentions, of foreign states regarding EMP attacks. The gamma pulse traveling outwards propagates at the speed of light, and the synchrotron radiation from the Compton electrons accumulates in a coherent way, producing a radiated electromagnetic signal. This interaction of negatively charged electrons with the magnetic field radiates a pulse of electromagnetic energy. However, it turns out that the real effects of an EMP in outer space on the power grid are strongly determined by the three-dimensional distribution of the rocks beneath our feet. Military tests to assess the survivability of EMPs may have been inaccurate, leading to incorrect conclusions about the effects of the electromagnetic pulse on commercial electronics. In July, Chinese researchers urged their government to increase the country's readiness to defend itself against a high-altitude EMP attack. Even a low-energy pulse has access to the power supply, and the pulse illuminates all parts of the system.
The immense potential of an EMP emitted by the detonation of a nuclear weapon at high altitude has long been recognized.