Apocalyptic Scenario #2

electromagnetic pulse (EMP)


Extreme electromagnetic incidents caused by an intentional electromagnetic pulse (EMP) attack or a naturally occurring geomagnetic disturbance (GMD, also referred to as “space weather”) could damage significant portions of the Nation’s critical infrastructure, including the electrical grid, communications equipment, water and wastewater systems, and transportation modes.

The impacts are likely to cascade, initially compromising one or more critical infrastructure sectors, spilling over into additional sectors, and expanding beyond the initial geographic regions.

EMPs are associated with intentional attacks using high-altitude nuclear detonations, specialized conventional munitions, or non-nuclear directed energy devices. Effects vary in scale from highly local to regional to continental, depending upon the specific characteristics of the weapon and the attack profile. High-altitude electromagnetic pulse attacks (HEMP) using nuclear weapons are of most concern because they may permanently damage or disable large sections of the national electric grid and other critical infrastructure control systems.

Similarly, extreme geomagnetic disturbances associated with solar coronal mass ejections (when plasma from the sun, with its embedded magnetic field, arrives at Earth) may cause widespread and long-lasting damage to electric power systems, satellites, electronic navigation systems, and undersea cables. Essentially, any electronics system that is not protected against extreme EMP or GMD events may be subject to either the direct “shock” of the blast itself or to the damage that is inflicted on the systems and controls upon which they are dependent. For these reasons, the potential severity of both the direct and indirect impacts of an EMP or GMD incident compels our national attention. 



In 2008, the Congressional Research Service, a public policy research arm of the United States Congress, defined Electromagnetic Pulse (EMP) as “an instantaneous, intense energy field that can overload or disrupt at a distance numerous electrical systems and high technology microcircuits, which are especially sensitive to power surges.”  An electromagnetic event can develop as a result of a result of a nuclear weapon detonated at high altitudes. The interaction between the Earth’s magnetic field and the high-energy particles from a nuclear EMP can result in serious damage to unhardened electrical infrastructure across large swathes of territory. An EMP can also be generated by portable high-power electromagnetic devices known as radio frequency weapons (RFWs) or by high-power microwave (HPM) weapons that can damage electronic systems over ranges from meters to kilometers.

Geomagnetic disturbance (GMD)

The term “GMD” refers to a geomagnetic disturbance caused by a solar storm or another naturally occurring phenomenon.  GMDs are caused by space weather events originating on the sun: naturally occurring sudden bursts of plasma and magnetic field structures (coronal mass ejections (CME) and bursts of radiation, or solar flares. These events tend to occur during the sun’s “solar maximum,” a four-to-six year period during the sun’s regular cycle of reversing the polarities of its north and south poles.

One to four days after an earth-directed flare or other eruption on the sun takes place, a GMD arrives at Earth and can cause multiple “space weather” effects.  This occurs when the CME interacts with the Earth’s electrojet and causes changes in the magnetic field. As the GMD field couples to conductive surfaces on the ground, effects are similar to a slow-pulse E3, particularly on long-line network systems, such as the electrical power grid, communications lines, and pipelines. The extent of this effect varies based on the size of the system, the frequency and magnitude of the field, and environmental factors.

Of particular concern, GMD events can cause widespread blackouts by producing electromagnetic fields that induce extreme currents in wires, disrupting power lines and damaging large, high-voltage transformers. GMDs have the potential to impact large areas of the earth.  Unlike EMP, however, GMD events occur with regularity, raising the issue of not “if,” but “when,” the next event will occur, and what the impacts may be.

EMP Attack (HEMP)

High-altitude EMP (HEMP) results from a nuclear detonation, delivered by ballistic missile or fractional-orbital satellite, occurring above an altitude 40 km. The range and amplitude of the resulting electromagnetic field is a function of the weapon’s payload and the height of the burst. For example, a powerful nuclear detonation 400 km over Kansas would likely adversely affect the entire continental U.S. However, if a nuclear device were detonated near the ground, the effective footprint of the EMP would be less than five miles in diameter, due to the limited range of gamma rays in the dense surrounding air. Nevertheless, currents resulting from a surface burst could affect systems out to as many as 80 km from the burst.