Electromagnetic pulse (EMP) and geomagnetic disturbance (GMD) events have the potential to cause serious disruption and damage to electrical components and entire systems in most critical infrastructure sectors. Whether caused by man or nature, these events can affect infrastructure on a large scale. While there is no evidence that EMP is a physical threat to humans, electrical or electronic systems, especially those connected to long cables such as power lines or antennas, can be damaged. This can result in actual physical damage to an electrical component or a temporary interruption in operation. An EMP, also known as transient electromagnetic disturbance (TED), is a brief burst of electromagnetic energy.
It can originate from either natural or artificial sources, and can occur as an electromagnetic field, an electric field, a magnetic field, or as a conducted electrical current. The interference caused by an EMP can interrupt communications and damage electronic equipment. An EMP, such as that of lightning, can even physically damage objects such as buildings and aircraft. Managing EMP effects is a branch of electromagnetic compatibility (EMC) engineering. A high-altitude electromagnetic pulse (HEMP) weapon is a NEMP warhead designed to detonate high above the Earth's surface.
This type of EMP can be caused by the detonation of a nuclear weapon, or naturally when the Sun emits a large current of plasma which interrupts the Earth's magnetic field. Induced pulses have much lower energy than threat pulses, so it's more practical to create them, but they are less predictable. High-altitude EMPS (HEMP), found twenty miles above Earth, usually send a pulse to any electrical connection present, in addition to radiating a pulse of energy. However, the pulses of a controlled switching circuit are usually in the form of a rectangular or square pulse. The concept of a flow compression generator with explosive pumping to generate a non-nuclear electromagnetic pulse was conceived as early as 1951 by Andrei Sakharov in the Soviet Union, but countries continued to work on the classification of non-nuclear EMPs until similar ideas emerged in other countries. Most electromagnetic pulses have a very sharp edge of attack and build up quickly to their maximum level.
To achieve the pulse frequency characteristics necessary for optimal coupling to the target, wave-forming circuits or microwave generators are added between the pulse source and the antenna. Natural electromagnetic pulses include lightning, coronal mass ejections (CME), and electrostatic discharges. Electromagnetic pulses from nuclear weapon detonations at altitudes of 30 to 400 kilometers (18 to 50 miles) can damage or destroy sensitive electronic equipment at ground level. A pulse of electromagnetic energy typically comprises many frequencies, from a very low limit to an upper limit, depending on the source. According to Maxwell's equations, a pulse of electrical energy will always be accompanied by a pulse of magnetic energy. The effects of E2 induction are similar to and are equivalent to the electromagnetic pulse that radiates from lightning bolts and that hits electronic devices and sensitive equipment during a shock.
The first recorded damage caused by an EMP occurred with the solar storm of August 1859, or the Carrington event.