Electromagnetic pulses (EMP) or transient electromagnetic disturbances (TED) can have devastating effects on semiconductor devices. When exposed to an EMP, these devices can fail due to the local heating that occurs, leading to the destruction of industrial processes, railway networks, electrical and telephone systems, and access to water supplies. Commercial IT equipment is especially vulnerable to the effects of EMP. Fortunately, there is no evidence that EMP is a physical threat to humans. However, electrical or electronic systems, particularly those connected to long cables such as power lines or antennas, can be damaged.
This damage can range from physical destruction of a component to a temporary interruption in its operation. A massive solar coronal mass ejection (CME) could shut down a significant fraction of the global power grid, but electronic devices not connected to the grid would not be affected. The electromagnetic pulse emitted by a nuclear explosion is very different because the first of its three phases occurs in billionths of a second. This extremely fast electromagnetic energy can travel hundreds of miles from an exploding nuclear bomb with a potential voltage of 50,000 volts or more per meter. This is far more than enough to permanently damage unshielded semiconductor electronic equipment.
The second phase of a nuclear bomb's EMP can also damage electronic components. The third phase is much slower and longer. The goal of an EMP attack is to cause widespread destruction by targeting thousands of miles of high-voltage power lines that serve as antennas. As Russia discovered during nuclear experiments in the 1960s, massive electrical currents absorbed by power lines can seriously damage high-voltage transformers and even entire power plants.
Contrary to popular belief, rebel states or terrorists do not need a sophisticated intercontinental ballistic missile to carry out an EMP attack.In reality, any missile, including short-range missiles that can launch a nuclear warhead at an altitude of 30 kilometers or more, can launch a catastrophic electromagnetic attack against the United States. This attack could be launched from a ship or freighter, making it difficult for forensic analysis to detect the source.
In fact, Iran has carried out EMP attacks launched from ships carrying Scud missiles, which are in the possession of dozens of countries and even terrorist groups. Unfortunately, most local and national government agencies in the United States are not prepared for an EMP attack. Some types of electromagnetic phenomena can leave an optical trail such as lightning and sparks, but these are side effects of the flow of current that circulates through the air and are not part of the EMP itself.