Electromagnetic pulses, common referred to as EMPs, are highly concentrated bursts of electromagnetic radiation. There are two primary ways in which an electromagnetic pulse is created, either by a solar storm, which releases charged solar gas, or by nuclear detonation. While EMPs caused by the sun happen somewhat frequently, there is often little to worry about. A man-made EMP could be a potential threat to the electronics and power grid of a metropolitan area.
The type of electromagnetic pules that are created by the sun are called CMEs, or Coronal Mass Ejections. These CMEs are usually caused by solar flares and activity which releases highly charged solar gases. This ejection of energy causes geomagnetic storms in Earth’s atmosphere, and occasionally these types of EMPs are strong enough to affect the planet. The two largest CMEs recorded occurred in 1859 and 1921 and, while they had little effect during that period, it is estimated that if CMEs of that strength occurred today, there would be significant damage to the power grid. A coronal mass ejection of this type did in fact strike Earth on March 9, 1989, causing a geomagnetic storm which knocked out power to the northern United States and Canada while also making the Northern Lights visible from Texas.
Electromagnetic pulses created by man usually occur in connection to a nuclear detonation, such as the July 1962 Starfish Prime test. This test created a high-altitude electromagnetic pulse, called a HEMP, which, although detonated over the Pacific, caused significant damage to Hawaii. The resulting pulse knocked out power and damaged electrical equipment. Although the damage caused by the 1.44 megaton blast was considered nominal, additional analysis showed that, if the blast had occurred over an area such as North America, the damage would have been greater due to the strength of Earth’s magnetic field over that location.
Factors that determine the strength of a HEMP include the yield of the blast, gamma ray output and the altitude of detonation. It is possible to shield electronics against any type of EMP; it involves the construction of a shield of multi-layer metals which can block the effects of the pulse. While the Earth is always subject to these types of pulses due to energy released from the sun, that energy often diffuses before striking the planet. A high-altitude electromagnetic pulse could cause a great amount of damage, however, especially considering the sensitivity of today’s electronics.
