Electromagnetic Pulse (EMP)
Following a Nuclear Detonation

• Source: [Text in this section adapted from Planning Guidance for Response to a Nuclear Detonation (May 2022) (fema.gov) (See pages 3, 6, 36, 41, 77, 117-118) (PDF - 2.62 MB) (National Security Staff, Interagency Policy Coordination Subcommittee for Preparedness & Response to Radiological and Nuclear Threats)]
  • Electromagnetic Pulse (EMP) is an intense pulse or surge of long wavelength radiofrequency electromagnetic radiation produced when an explosion occurs near the earth’s surface or at high altitudes
  • EMP occurs at the instant of the detonation of an IND and ends within a few seconds
  • For large, high-altitude bursts (greater than 5km above ground level) the electric fields generated in high-altitude EMP are complex and may exist over a large area (perhaps the size of Nebraska or larger), damaging or disrupting unprotected electronic devices. but it is not well understood how it radiates outward from a ground level burst and to what degree it will damage the electronic systems that permeate modern society.
  • A Source-Region Electromagnetic Pulse (SREMP) is generated in the region near low-altitude nuclear detonations (<5km above ground level). SREMP is a very short-duration, high-amplitude electric field that falls off rapidly with distance from detonation.
  • SREMP impacts electronic equipment through two ways: induced voltage on internal wires and conducting materials (including pipes), and large voltage/current surges in long power lines and other conducting materials that pass near detonation. This can propagate for significant distances, resulting in disruption and potential damage a few miles outside of the blast damage area.
  • Although experts have not achieved consensus on expected impacts, generally they believe that the most severe consequence of the pulse would not travel beyond about 2 miles (3.2 km) to 5 miles (8 km) from a ground level 10 KT IND detonation.
  • Because the extent of the EMP damage to communications and electronics is expected to occur relatively close to ground zero, other infrastructure effects of the explosion (such as blast destruction) are expected to dominate over the EMP effect.
  • Equipment brought in from unaffected areas should function normally if communications towers and repeaters remain functioning, but these towers and repeaters may be severely damaged by the blast and could be offline for that reason.
• Effect on health
  • The EMP associated with a nuclear detonation poses no direct health threat, although health-related equipment may be affected.
• Effects on equipment
  • Intense electric and magnetic fields of an EMP can damage unprotected electronic equipment over a large area.
    • Communications infrastructure (cell towers, telecommunications switches, dishes, radar) will be significantly affected.
    • Disruption of the electrical grid and electronic equipment is greatest nearest the ground zero of the detonation.
    • Potential extensive electronics disruptions will complicate the function of communications, computers and computer systems, and other essential electronic equipment, including key hospital equipment, gas stations, and other electrical components of the region's key critical infrastructure.
    • Other EMP related equipment effects might include stalling of vehicles (from effects on vehicle electronics) and water and electrical system control components destroyed or disrupted.
• Effects on communications infrastructure
  • Communications and other electronic equipment brought in from unaffected areas should function normally if communications towers and repeaters in the infrastructure remain functioning.
  • Cell phones and handheld radios have relatively small antennas. If they are not connected to electrical power supplies during the electromagnetic pulse (EMP) they may not be affected, but they do rely on an intact infrastructure for communications.
• Effects on the response
  • Communications: The effectiveness of protective action recommendations (e.g., shelter-in-place, and all clear from shelter in place) depends on the ability to communicate with responders and the public. Planners should specifically consider communications problems that will be caused by a nuclear detonation (e.g., EMP and infrastructure damage) and recognize in their planning that normal means of communication may not be available. Mass communication methods and public guidance on stocking of battery-powered radios may be appropriate.
  • Response capabilities: Infrastructure more than five miles away from ground zero are likely to be only nominally affected by blast and EMP of a 10kT device and should be able to mobilize and respond, provided they are not within the path of dangerous fallout levels.
  • Blast Damage Zones: There will be minimal, if any, ability to send or receive information in the blast damage zones (LD, MD and SD zones). It may be days before communications capabilities are re-established. Within this area, all communications capabilities will be destroyed or severely hindered. The blast will cause physical damage to communications systems – electrical, phone and cellular systems will be down.
  • Surrounding Area (beyond the LD, MD, and SD zone areas) The surrounding area includes surrounding communities, counties, bordering states, and people in the path of the radioactive plume, including the DF zone. After a nuclear detonation, there is the potential for cascading effects along transmission lines in this area. This could mean electrical, phone, and Internet outages. These cascading effects may extend for hundreds of miles from the detonation site. The EMP should have limited, if any, effect on electronic devices in the surrounding area and DF zone outside of the blast damage zone. Electronic devices may only require resetting switches and circuit breakers.

Key References for EMP

1. Planning Guidance for Response to a Nuclear Detonation (May 2022) (fema.gov) (PDF - 2.62 MB) [See pages 3, 6, 36, 41, 77, 117-118] (National Security Staff, Interagency Policy Coordination Subcommittee for Preparedness & Response to Radiological and Nuclear Threats)
2. Critical Infrastructure Protection: Federal Agencies Have Taken Actions to Address Electromagnetic Risks, but Opportunities Exist to Further Assess Risks and Strengthen Collaboration See all 3 tabs: Highlights, Recommendations, View Report (63 pages). (US Government Accountability Office, GAO-16-243, March 2016)
3. Presidential Executive Order 13865—Coordinating National Resilience to Electromagnetic Pulses, March 26, 2019 (PDF - 186 KB) (Government Publishing Office)
4. Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack
   • April 2008 Report (PDF - 7.3 MB)
   • Executive Report: Volume 1, 2004: see “Strategy and Recommendations”: page 11 (PDF - 578 KB)
5. Glasstone S, Dolan PJ, The Effects of Nuclear Weapons, (PDF - 31 MB), 3rd ed. Washington, D.C.: US Government Printing Office, 1977. See Chapter XI, The Electromagnetic Pulse and its Effects, pages 514-540.