An Electromagnetic Pulse (EMP) refers to a short burst of electromagnetic energy that can have destructive effects on electrical and electronic devices. EMP can be generated by various sources, including nuclear explosions, solar flares, and high-altitude detonations of nuclear weapons.

When a large amount of electromagnetic energy is released, it interacts with the atmosphere, causing electrons to become dislodged from atoms. These electrons, guided by the Earth's magnetic field, form a massive and powerful circuit. As this circuit flows through the atmosphere, it generates strong electromagnetic fields that spread to the Earth's surface. When these fields come into contact with conductive materials, such as those found in electronic devices, they transfer energy into the materials. If the density of this energy is high enough, it can severely damage or destroy the electronic device.

There are two primary types of EMP:

High-altitude EMP (HEMP):

This type of EMP occurs when a nuclear weapon is detonated at altitudes above the Earth's atmosphere. The detonation releases intense gamma radiation, which interacts with the Earth's magnetic field, producing a powerful electromagnetic field. This electromagnetic field can induce high voltages and currents in electrical and electronic systems on the ground, potentially damaging or disabling them. The frequency range of HEMP typically covers a wide spectrum, ranging from very low frequencies (VLF) to extremely high frequencies (EHF) [few hundred MHz].

The electromagnetic pulse (EMP) generated can reach incredibly high intensities, reaching up to 50,000 volts per meter (V/m). These are quite common in military scenarios due to which hardening of equipment is carried out. In military applications, it is common to enclose systems within fully-shielded environments made of highly conductive materials like steel. These environments are designed with specific penetrations to maintain RF shielding while allowing for system functionality.

Non-nuclear EMP:

Non-nuclear EMPs(NNEMPs) are generated by devices that emit electromagnetic radiation without the need for a nuclear explosion. These devices typically use high-power microwave sources or other electromagnetic radiation sources to generate a short but powerful burst of energy.

Some of these devices include:

Large low-inductance capacitor bank: This is a bank of capacitors that stores a significant amount of electrical energy. When discharged, it releases a sudden surge of electrical current.

Single-loop antenna: This is an antenna designed to efficiently radiate the electromagnetic pulse into the surrounding area.

Microwave generator: A device that generates high-frequency microwave energy, which can be used to enhance the characteristics of the pulse.

Explosively pumped flux compression generator: This is a device that uses explosives to compress a magnetic field, resulting in a powerful electromagnetic pulse.

Non-nuclear EMPs can be created intentionally for military or research purposes, or they can occur unintentionally as a result of natural or man-made events.

To optimize the pulse's ability to couple with the target, additional circuits or microwave generators are used to shape the waveform or adjust the frequency. Vircators, which are vacuum tubes, are often employed for converting high-energy pulses into microwave frequencies.

The effects of EMP can vary depending on the strength and proximity of the pulse, as well as the vulnerability of the affected devices. In severe cases, EMP can disrupt or destroy electronic equipment, including power grids, communication systems, computers, and other electronic devices. This potential for widespread disruption has led to concerns about the vulnerability of critical infrastructure to EMP events and efforts to develop protective measures. The use of an electromagnetic pulse (EMP) as a potential threat is a modern version of a longstanding danger associated with nuclear warfare. While some experts may doubt the likelihood of a foreign adversary relying solely on an EMP to cripple the national power grid, it is important to recognize that the broader threat of a nuclear attack should not be disregarded.