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An electromagnetic pulse (EMP) is a short burst of electromagnetic energy interference caused by an abrupt and rapid acceleration of charged particles, which can damage electronic components by short-circuiting them. An EMP can contain many energy components of the electromagnetic spectrum, from the very low frequency waves to the ultraviolet wavelengths. One very common cause of EMP is lightning strikes, which supercharge ions in the atmosphere and cause electricity in the power lines to surge.
An EMP or transient electromagnetic disturbance is a fairly natural phenomenon, with lightning being the most common cause of fairly low energy pulses that cause localized electrical surges and short circuits in unshielded devices, apart from the damage caused by the lightning strike itself. EMP interference is already generally disruptive to electronic equipment at very low levels, such as causing corrupted data and crosstalk between wired media. Electric motors generate train pulses as the internal contacts rotate, and even the constant switching digital circuitry causes low-level interference that may still be detrimental to other electronic components in its vicinity, which is why shielding is already a major part in the design of electronic hardware.
Massive energy-level EMP is produced regularly by the Sun as solar magnetic flares, but the Earth's magnetic field protects it from this phenomenon. Similarly, high-energy EMP can be generated by a nuclear blast (electromagnetic bomb), which becomes worse the higher the blast occurs because its range becomes greater. A nuclear explosion produces EMP through the emission of gamma rays, which are converted into EMP in the Earth's mid-stratosphere and affects a wide area along the line of sight of the explosion.