The term electromagnetic pulse (EMP) has the following meanings:

1. electromagnetic radiation from an explosion (especially a nuclear explosion) or an intensely fluctuating magnetic field caused by Compton-recoil electrons and photoelectrons from photons scattered in the materials of the electronic or explosive device or in a surrounding medium. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. An explosion is a sudden increase in Volume and release of Energy in an extreme manner usually with the generation of high Temperatures and the release A nuclear explosion occurs as a result of the rapid release of energy from an intentionally high-speed Nuclear reaction. In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges The Compton shift formula Klein-Nishina formulaCompton used a combination of three fundamental formulas representing the various aspects of classical and modern physics combining The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Introduction When a Metallic surface is exposed to Electromagnetic radiation above a certain threshold Frequency, the light is absorbed and Electrons In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Scattering is a general physical process whereby some forms of Radiation, such as Light, Sound or moving particles for example are forced to deviate from A transmission medium' (plural transmission media) is a material substance ( Solid, Liquid or Gas) which can propagate The resulting electric and magnetic fields may couple with electrical/electronic systems to produce damaging current and voltage surges. In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can In electrical engineering spikes are fast short duration electrical transients in voltage ( voltage spikes) current ( current spike) or transferred energy See Electromagnetic bomb for details on the damages resulting to electronic devices. An electromagnetic bomb or E-bomb is a weapon designed to disable electronics with an Electromagnetic pulse (EMP that can couple with electrical/electronic systems The effects are usually not noticeable beyond the blast radius unless the device is nuclear or specifically designed to produce an electromagnetic shockwave. The energy released from a nuclear weapon detonated in the Troposphere can be divided into four basic categories Blast &mdash40-50% of total energy
2. A broadband, high-intensity, short-duration burst of electromagnetic energy. In Physics, intensity is a measure of the time-averaged Energy Flux.

In the case of a nuclear detonation or an asteroid impact, most of the energy of the electromagnetic pulse is distributed in the frequency band between 3 Hz and 30 kHz. In Medicine, a person's pulse is the throbbing of their arteries. Frequency is a measure of the number of occurrences of a repeating event per unit Time.

Practical considerations

The mechanism for a 400 km high altitude burst EMP: gamma rays hit the atmosphere between 20–40 km altitude, ejecting electrons which are then deflected sideways by the earth's magnetic field. This makes the electrons radiate EMP over a massive area. Because of the curvature of earth's magnetic field over the USA, the maximum EMP occurs south of the detonation and the minimum occurs to the north.

The worst of the pulse lasts for only a second, but any unprotected electrical equipment — and anything connected to electrical cables, which act as giant lightning rods or antennas — will be affected by the pulse. A lightning rod (USA or lightning conductor (UK is a single component in a Lightning protection system. An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into Older, vacuum tube (valve) based equipment is much less vulnerable to EMP; Soviet Cold War–era military aircraft often had avionics based on vacuum tubes. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 Cold War is the state of conflict tension and competition that existed between the United States and the Soviet Union (USSR and their respective allies from the There are a number of websites that explore methods for protecting equipment in the home or business from the effects of an EMP attack.

Many nuclear detonations have taken place using bombs dropped by aircraft. The aircraft that delivered the atomic weapons at Hiroshima and Nagasaki did not fall out of the sky due to damage to their electrical or electronic systems. The Japanese city of ( is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshū, the largest of Japan 's ( is the Capital and the largest city of Nagasaki Prefecture in Japan. This is simply because electrons (ejected from the air by gamma rays) are stopped quickly in normal air for bursts below 10 km, so they do not get a chance to be significantly deflected by the Earth's magnetic field (the deflection causes the powerful EMP seen in high altitude bursts), but it does point out the limited use of smaller burst altitudes for widespread EMP. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Earth 's magnetic field (and the surface magnetic field) is approximately a Magnetic dipole, with one pole near the North pole (see

If the B-29 planes had been within the intense nuclear radiation zone when the bombs exploded over Hiroshima and Nagasaki, then they would have suffered effects from the charge separation (radial) EMP. Photoinduced charge separation is the process of an Electron in an Atom being excited to a higher energy level and then leaving the atom to a nearby Electron But this only occurs within the severe blast radius for detonations below about 10 km altitude. EMP disruptions were suffered aboard KC-135 photographic aircraft flying 300 km from the 410 kt Bluegill and 410 kt Kingfish detonations (48 and 95 km burst altitude, respectively) in 1962 [1], but the vital aircraft electronics then were far less sophisticated than today and did not crash the aircraft. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Operation Dominic was a series of 105 Nuclear test explosions conducted in 1962 and 1963 by the United States. Operation Dominic was a series of 105 Nuclear test explosions conducted in 1962 and 1963 by the United States.

Several major factors control the effectiveness of an EMP weapon. These are:

1. The altitude of the weapon when detonated;
2. The yield of the weapon;
3. The distance from the weapon when detonated;
4. Geographical depth or intervening geographical features. The explosive yield of a nuclear weapon is the amount of Energy, called the Yield, discharged when a Nuclear weapon is detonated expressed usually

Beyond a certain altitude a nuclear weapon will not produce any EMP, as the gamma rays will have had sufficient distance to disperse. In deep space or on worlds with no magnetic field (the moon or Mars for example) there will be little or no EMP. This has implications for certain kinds of nuclear rocket engines. See Project Orion. Project Orion was the first engineering design study of a Spacecraft powered by Nuclear pulse propulsion, an idea first proposed by Stanisław Ulam

Weapon altitude

How the peak EMP on the ground varies with the weapon yield and burst altitude. The yield here is the prompt gamma ray output measured in kilotons. This varies from 0. 115–0. 5% of the total weapon yield, depending on weapon design. The 1. 4 Mt total yield 1962 Starfish Prime test had an output of 0. Starfish Prime was a high-altitude nuclear test conducted by the United States of America on July 9, 1962, a joint effort of the 1%, hence 1. 4 kt of prompt gamma rays. (The blue 'pre-ionisation' curve applies to certain types of thermonuclear weapon, where gamma and x-rays from the primary fission stage ionise the atmosphere and make it electrically conductive before the main pulse from the thermonuclear stage. Nuclear weapon designs are physical chemical and engineering arrangements that cause the physics package of a nuclear weapon to detonate Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions X-radiation (composed of X-rays) is a form of Electromagnetic radiation. Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons The pre-ionisation in some situations can literally short out part of the final EMP, by allowing a conduction current to immediately oppose the Compton current of electrons. )

According to an internet primer published by the Federation of American Scientists^[1]

A high-altitude nuclear detonation produces an immediate flux of gamma rays from the nuclear reactions within the device. The Federation of American Scientists ( FAS) is a non-profit organization formed in 1945 by scientists from the Manhattan Project who felt that scientists engineers In the various subfields of Physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions These photons in turn produce high energy free electrons by Compton scattering at altitudes between (roughly) 20 and 40 km. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The Compton shift formula Klein-Nishina formulaCompton used a combination of three fundamental formulas representing the various aspects of classical and modern physics combining These electrons are then trapped in the Earth's magnetic field, giving rise to an oscillating electric current. Earth 's magnetic field (and the surface magnetic field) is approximately a Magnetic dipole, with one pole near the North pole (see Oscillation is the repetitive variation typically in Time, of some measure about a central value (often a point of Equilibrium) or between two or more different states Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. This current is asymmetric in general and gives rise to a rapidly rising radiated electromagnetic field called an electromagnetic pulse (EMP). The electromagnetic field is a physical field produced by electrically charged objects. Because the electrons are trapped essentially simultaneously, a very large electromagnetic source radiates coherently. In Physics, coherence is a property of waves that enables stationary (i

The pulse can easily span continent-sized areas, and this radiation can affect systems on land, sea, and air. The first recorded EMP incident accompanied a high-altitude nuclear test over the South Pacific and resulted in power system failures as far away as Hawaii. Australasia is a Region of Oceania: New Zealand, Australia, Papua New Guinea, and neighbouring Islands in the Pacific The State of Hawaii ( or həˈwaɪʔiː Hawaiian: Mokuāina o Hawaii) is a state in the United States located on an Archipelago in the A large device detonated at 400–500 km (250 to 312 miles) over Kansas would affect all of the continental U. Kansas ( is a Midwestern state in the central region of the United States of America, an area often referred to as the American " S. The signal from such an event extends to the visual horizon as seen from the burst point.

Thus, for equipment to be affected, the weapon needs to be above the visual horizon. The horizon ( Ancient Greek ὁ ὁρίζων, /ho horídzôn/ from ὁρίζειν, "to limit" is the apparent line that separates Because of the nature of the pulse as a large, long, high powered, noisy spike, it is doubtful that there would be much protection if the explosion were seen in the sky just below the tops of hills or mountains. In electrical engineering spikes are fast short duration electrical transients in voltage ( voltage spikes) current ( current spike) or transferred energy

The altitude indicated above is greater than that of the International Space Station and many low Earth orbit satellites. A Low Earth Orbit (LEO is generally defined as an Orbit within the locus extending from the Earth’s surface up to an altitude of 2000 km Large weapons could have a dramatic impact on satellite operations and communications; smaller weapons have less such potential. This article is about artificial satellites For natural satellites also known as moons see Natural satellite.

Weapon yield

Typical nuclear weapon yields quoted in such scenarios are in the range of 20 megatons. The explosive yield of a nuclear weapon is the amount of Energy, called the Yield, discharged when a Nuclear weapon is detonated expressed usually This is roughly 1,000 times the sizes of the weapons the United States used in Japan at Hiroshima and Nagasaki. The United States of America —commonly referred to as the For a topic outline on this subject see List of basic Japan topics. The Japanese city of ( is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshū, the largest of Japan 's ( is the Capital and the largest city of Nagasaki Prefecture in Japan.

Weapon distance

The major energy in an EMP is electromagnetic, and radiates out from the point of detonation in a sphere. EMP is electromagnetic radiation. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. The intensity of these fields decreases in proportion to the circumference and distance from explosion. The actual amount of EMP energy deposited per unit area is entirely different, and that falls off as the inverse-square of distance.

How the area affected depends on the burst altitude.

The range of deposition of gamma rays would be smaller for a surface burst because of the greater air density, which shields the initial gamma rays that cause the EMP. Conversely, for a burst at greater altitudes, the range of the deposition would be far greater than 10 miles, because the gamma rays could travel much further in the low density air before being stopped. The actual energy deposited per unit area, if emitted from an isotropic point source, is always governed by the inverse-square law. A point source is a single identifiable localized source of something

But the damaging effect of EMP is determined largely by the peak electric field (measured in volts/metre), which falls only inversely with distance. The amount of EMP energy passing through a unit of area is proportional to the square of the field strength. In Physics, the field strength of a field is the magnitude of its vector value Within the range of gamma ray deposition, these simple laws no longer hold as the air is ionised and there are other EMP effects such as a radial (non-radiated) electric field due to the separation of Compton electrons from air molecules, and other complex phenomena. Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons so its energy = 1/d^2

Non-nuclear electromagnetic pulse

A right front view of a Boeing E-4 advanced airborne command post (AABNCP) on the electromagnetic pulse (EMP) simulator for testing. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout

Non-nuclear electromagnetic pulse (NNEMP) is an electromagnetic pulse generated without use of nuclear weapons. There are a number of devices to achieve this objective, ranging from a large low-inductance capacitor bank discharged into a single-loop antenna or a microwave generator to an explosively pumped flux compression generator. A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors An explosively pumped flux compression generator (EPFCG is a device used to generate a high-power Electromagnetic pulse by compressing magnetic flux using High explosive To achieve the frequency characteristics of the pulse needed for optimal coupling into the target, wave-shaping circuits and/or microwave generators are added between the pulse source and the antenna. In Electronics and Telecommunication, coupling is the desirable or undesirable Transfer of energy from one medium, such as a metallic wire or An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into A vacuum tube particularly suitable for microwave conversion of high energy pulses is the vircator. A vircator (VIRtual CAthode OscillatOR is a Microwave generator that is capable of generating brief pulses of tunable narrow band microwaves at very high power levels

USS Estocin (FFG-15) moored near an Electro Magnetic Pulse Radiation Environmental Simulator for Ships I (EMPRESS I) facility. (Antennae at top of image)

NNEMP generators can be carried as a payload of bombs and cruise missiles, allowing construction of electromagnetic bombs with diminished mechanical, thermal and ionizing radiation effects and without the political consequences of deploying nuclear weapons. A cruise missile is a guided Missile that carries an explosive payload and uses a lifting wing and a propulsion system usually a Jet engine, to allow An electromagnetic bomb or E-bomb is a weapon designed to disable electronics with an Electromagnetic pulse (EMP that can couple with electrical/electronic systems

NNEMP generators also include large structures built to generate EMP for testing of electronics to determine how well it survives EMP. In addition, the use of ultra-wideband radars can generate EMP in areas immediately adjacent to the radar; this phenomenon is only partly understood.

Modern scenarios

Typical modern scenarios seen in news accounts speculate about the use of nuclear weapons by rogue states or terrorists in an attack. Terrorism is the systematic use of terror especially as a means of coercion These typically involve weapons similar to those used over Hiroshima and Nagasaki. Aerial detonation would require the use of aircraft, or surface launched missiles of limited range (typically a range 100 to 300 miles). A surface to air missile ( SAM) or ground-to-air missile ( GTAM) is a Missile designed to be launched from the ground to destroy Aircraft The scenarios have the detonations typically occurring within the earth's atmosphere, and likely relatively close to the ground (within a dozen or so miles).

This would limit the EMP effect because the altitude of the explosion would be much lower than that needed to be above the visual horizon of the entire United States. Also, the power of the weapons would typically be hundreds if not thousands of times smaller than optimum, and thus the effect would be significantly smaller than that of a larger weapon.

However, the EMP at a fixed distance from a nuclear weapon does not depend directly on the yield but at most only increases as the square root of the yield (see illustration above). This means that although a 10 kt weapon has only 0. 7% of the total energy release of the 1. 4 Mt Starfish Prime test, the EMP will be at least 8% as powerful. Starfish Prime was a high-altitude nuclear test conducted by the United States of America on July 9, 1962, a joint effort of the Since the EMP depends on the prompt gamma ray output, which was only 0. 1% of yield in Starfish Prime but can be 0. Starfish Prime was a high-altitude nuclear test conducted by the United States of America on July 9, 1962, a joint effort of the 5% of yield in pure fission weapons of low yield, a 10 kt bomb can easily be 5 x 8% = 40% as powerful as the 1. 4 Mt Starfish Prime at producing EMP [2]. Starfish Prime was a high-altitude nuclear test conducted by the United States of America on July 9, 1962, a joint effort of the

The total prompt gamma ray energy in a fission explosion is 3. 5% of the yield, but in a 10 kt detonation the high explosive around the bomb core absorbs about 85% of the prompt gamma rays, so the output is only about 0. 5% of the yield in kilotons. In the thermonuclear Starfish Prime the fission yield was less than 100% to begin with, and then the thicker outer casing absorbed about 95% of the prompt gamma rays from the pusher around the fusion stage. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus Starfish Prime was a high-altitude nuclear test conducted by the United States of America on July 9, 1962, a joint effort of the Thermonuclear weapons are also less efficient at producing EMP because the first stage can pre-ionise the air [3], which becomes conductive and hence rapidly shorts out the electron Compton currents generated by the final, larger yield thermonuclear stage. Nuclear weapon designs are physical chemical and engineering arrangements that cause the physics package of a nuclear weapon to detonate The Compton shift formula Klein-Nishina formulaCompton used a combination of three fundamental formulas representing the various aspects of classical and modern physics combining Hence, small pure fission weapons with thin cases are far more efficient at causing EMP than most megaton bombs.

A terrorist EMP attack might profoundly affect any major city; however, because of the high cost of real estate and traffic issues, many major businesses have relocated valuable assets outside of major urban areas, and have taken other measures to protect themselves. Therefore, the long-term economic and technological impact of such an event might not be as grave as previously imagined, depending on the nature of the original attack.

A common scenario is detonation of a device over the middle of the U. S. using long-range missiles available only to major military powers. An offshore detonation at high altitude, by contrast, would present less technical difficulty and would disrupt both an entire coast and regions hundreds of miles inland (e. g. 120 mile altitude, 1000 mile EMP radius). The term electromagnetic pulse ( EMP) has the following meanings Electromagnetic radiation from an Explosion (especially a Nuclear Moreover, a high altitude burst could be positioned over international waters by means of a missile of low accuracy, launched from a ship, also in international waters. North Korea, Iran, and Pakistan (for example) have Scud-derived missiles of more than adequate capability. The Rodong-1 (spelled Nodong-1 in South Korea is a single stage, mobile liquid propellant medium range Ballistic missile developed by North The Shahab-2 ( Persian: شهاب-۲ meaning "Meteor-2" is the successor to the Iranian Shahab-1 missile Ghauri (غوری is a Medium-range ballistic missile developed by Kahuta Research Laboratories (KRL of Pakistan. Scud is a series of Tactical ballistic missiles developed by the Soviet Union during the Cold War and exported widely to other countries

References

1. ^ Nuclear Weapon EMP Effects

See also

• High Energy Radio Frequency weapons (HERF)
• Explosively pumped flux compression generator
• Transient electromagnetic device
• Electromagnetic environment
• Electromagnetic propulsion
• Electromagnetic bomb
• Electromagnetism
• Pulsed power
• Neutron flux

External links

• GlobalSecurity.org – Electromagnetic Pulse: From chaos to a manageable solution
• Electromagnetic Pulse (EMP) and Tempest Protection for Facilities – U. High Energy Radio Frequency weapons (HERF or High Power Radio Frequency weapons (HPRF are weapons that use high intensity radio waves to disrupt Electronics An explosively pumped flux compression generator (EPFCG is a device used to generate a high-power Electromagnetic pulse by compressing magnetic flux using High explosive An electromagnetic bomb or E-bomb is a weapon designed to disable electronics with an Electromagnetic pulse (EMP that can couple with electrical/electronic systems In Telecommunication, the term electromagnetic environment (EME has the following meanings 1 Electromagnetic propulsion uses the concepts and applications of Electromagnets It includes the class of experiments and theories that have been examined for the development An electromagnetic bomb or E-bomb is a weapon designed to disable electronics with an Electromagnetic pulse (EMP that can couple with electrical/electronic systems Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of Pulsed power is the term used to describe the science and technology of accumulating Energy over a relatively long period of time and releasing it very quickly thus increasing Neutron flux is a term referring to the number of Neutrons passing through an Area over a span of Time. S. Army Corps of Engineers
• EMP data from Starfish nuclear test measured by Richard Wakefield of LANL, and review of evidence pertaining to the effects 1,300 km away in Hawaii, also review of Russian EMP tests of 1962

• Pulse Counter