Electromagnetic pulse

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An electromagnetic pulse (EMP), also sometimes called a transient disturbance, is a short burst of electromagnetic energy. It may occur in the form of a radiated, electric or magnetic field or conducted electrical current depending on the source. Electromagnetic pulse is commonly abbreviated EMP, pronounced by saying the letters separately (E-M-P).

EMP is generally damaging to electronic equipment, and its management is an important branch of electromagnetic compatibility (EMC) engineering. At higher energy levels, an EMP event such as a lightning strike can cause more widespread damage to aircraft structures and other objects.

The damaging effects of high-energy EMP have been used to create EMP weapons, both nuclear and non-nuclear. These weapons, both real and fictional, have gained traction in popular culture.

General characteristics[edit]

An electromagnetic pulse is a relatively short burst of electromagnetic energy. Its shortness means that it will always be spread over a range of frequencies. Pulses are typically characterised by:

  • The type of energy (radiated, electrical, magnetic or conducted).
  • The range of frequencies present.
  • Pulse envelope or waveform, duration and amplitude.

Types of energy[edit]


  • Electric field
  • Magnetic field
  • Electromagnetic radiation
  • Electrical conduction


Frequency ranges[edit]


The highest frequencies are generated by NEMP bursts and continue up into the optical and ionizing ranges. Other types can leave a visible trail, such as lightning and sparks, but these are side effects of the current flow through the air and are not part of the EMP itself.

Pulse waveforms[edit]

The waveform of a pulse describes how its amplitude changes over time. Real pulses tend to be quite complicated, so simplified models are often used. Such a model is typically shown either as a diagram or as a mathematical equation.

" "
Rectangular pulse
" "
Double exponential pulse
" "
Damped sinewave pulse

Most pulses have a very sharp leading edge, building up quickly to their maximum level. The classic model is a double-exponential curve which climbs steeply, quickly reaches a peak and then decays more slowly. However pulses from a controlled switching circuit often take the form of a rectangular or "square" pulse.




Minor EMP events, and especially pulse trains, cause low levels of electrical noise or interference which can affect the operation of susceptible devices. For example a common problem in the mid-twentieth century was the interference emitted by the ignition systems of gasoline engines, which caused radio sets to crackle and TV sets to show stripes on the screen. Laws had to be introduced to make vehicle manufacturers fit interference suppressors.

At a higher level an EMP can induce a spark, for example when fuelling a gasoline-engined vehicle, such sparks have been known to cause fuel-air explosions and precautions must be taken to prevent them.

The direct effect of a very large EMP is to induce high currents and voltages in the victim, damaging electrical equipment or disrupting its function. A very large EMP event such as a lightning strike is also capable of damaging objects such as trees, buildings and aircraft directly, either through heating effects or the disruptive effects of the very large magnetic field generated by the current. An indirect effect can be electrical fires caused by the heating. Most engineered structures and systems require some form of protection against lightning to be designed in. These damaging effects have led to the introduction of EMP weapons.

Types of EMP[edit]


Types of EMP divide broadly into natural, man-made and weapons effects.

Types of natural EMP event include:


Types of (civilian) man-made EMP event include:

  • Continual switching actions of digital electronic circuitry.

Types of military EMP include:

  • Non-nuclear electromagnetic pulse (NNEMP) weapons.



Electrostatic discharge (ESD)[edit]



Switching pulses[edit]








Non-nuclear electromagnetic pulse (NNEMP)[edit]

A National Airborne Operations Center Boeing E-4on EMP simulator HAGII-C for testing.
USS Estocin (FFG-15) moored near EMPRESS I. (antennae at top of image).




The concept of the explosively pumped flux compression generator for generating a non-nuclear electromagnetic pulse was conceived as early as 1951 by Andrei Sakharov in the Soviet Union,[7] but nations keep work on non-nuclear EMP classified until similar ideas emerge in other nations.

Electromagnetic forming[edit]






Test simulation[edit]


A small-scale ESD simulator may be hand-held.

At the other end of the scale, large outdoor test facilities incorporating high-energy EMP simulators have been built in the United States, the Soviet Union, the United Kingdom, France, Germany, the Netherlands, Switzerland and Italy.[8][9] The largest facilities are able to test whole vehicles including ships and aircraft for their susceptibility to EMP.

Information about the EMP simulators used by the United States during the latter part of the Cold War, along with more general information about electromagnetic pulse, is now in papers under the care of the SUMMA Foundation,[10] which is hosted at the University of New Mexico.

The SUMMA Foundation web site documents the huge wooden ATLAS-I simulator (better known as TRESTLE, or "The Sandia Trestle") at Sandia National Labs, New Mexico, which was the world's largest EMP simulator.[11]  Nearly all of these large EMP simulators used a specialized version of a Marx generator.[8][9] The SUMMA Foundation offers a short documentary on its web site called TRESTLE: Landmark of the Cold War.[12]

The US Navy also has a facility called the Electro Magnetic Pulse Radiation Environmental Simulator for Ships I (EMPRESS I).

EMP in fiction and popular culture[edit]


References to EMP weapons in popular fiction go back at least to 1965, however EMP did not gain a significant presence until the mid 1980s.



  4. ^ Glasstone & Dolan 1977, Chapter 1.
  7. ^ Stephen Younger, et al. (1996). "Scientific Collaborations Between Los Alamos and Arzamas-16 Using Explosive-Driven Flux Compression Generators". Los Alamos Science (24,): 48–71. Retrieved 2009-10-24. 
  12. ^ TRESTLE: Landmark of the Cold War (Documentary Movie)
  14. ^ 2009 Telly Award Winners, (Manitou Motion Picture Company, Ltd.) [2] The U.S. Space Command video is not available to the general public.


See also[edit]