Nuclear electromagnetic pulse (EMP)

A nuclear electromagnetic pulse (EMP) is a burst of electromagnetic energy that results from a nuclear explosion. An EMP can be caused by a nuclear weapon or can originate from the sun during a time of extreme solar activity. The electrical charge released by the process has the potential to cause widespread damage to electronic equipment and power lines, raising fears that such an occurrence could lead to a catastrophic disruption in communication and energy systems. EMPs have affected human activity in the past. In the 1960s, a nuclear weapons test shorted out streetlights in Hawaii, and in 1989, a solar storm caused a large blackout over parts of Canada.

Discovery and Cause of an EMP

American physicist Arthur Compton first observed the science behind an electromagnetic pulse in the 1920s while studying the properties of light. The light visible to the human eye is just one part of the electromagnetic spectrum. Light at the infrared end of the spectrum, such as radio waves or microwaves, travels at longer wavelengths and lower frequencies. Light at the ultraviolet end, such as X-rays and gamma rays, has shorter wavelengths and higher frequencies. Compton noticed that photons (particles of light) from X-rays that were shot at a metal surface scattered into longer wavelengths. This was because the photons transferred part of their energy to the electrons in the metal and knocked some of them free. The process became known as the Compton effect and earned its namesake the 1927 Nobel Prize in Physics.

A nuclear explosion produces high-frequency gamma rays that can knock loose electrons from atoms in the atmosphere. These free electrons can cause a burst of charged electrical particles that travels at the speed of light and can short out electronic components and wiring.

When the United States first began testing nuclear weapons in 1945, scientists expected some form of EMP effect and took precautions to safeguard against it. They were unaware of the extent of an EMP at high altitudes until they began atmospheric tests of nuclear weapons in the late 1950s and early 1960s. In July 1962, the United States detonated a thermonuclear device about 250 miles above the Pacific Ocean. The test, code-named Starfish Prime, produced an explosion much larger than scientists expected and created an EMP that knocked out streetlights and damaged phone lines in Hawaii, almost 900 miles away. A Soviet EMP test later that year burned out power lines and caused electrical fires in a city in central Kazakhstan.

An EMP from a nuclear weapon consists of three components. The most damaging is called E1, an extremely fast pulse that generates a devastating electrical charge; an E2 pulse is similar to the charge produced by lightning and is easier to protect against; an E3 pulse is a slower electrical surge produced by the blast moving Earth's magnetic field.

Effects from a Nuclear Device

Scientists continued to study high-altitude EMPs and quickly realized the effect could be used as a weapon. During the Cold War, the United States feared the Soviet Union would detonate a nuclear device above the country and damage US electrical equipment. Such an event would have had severe consequences, but the technology of the 1960s would have actually helped minimize EMP damage. Electrical devices of the era were less advanced and relied on fewer electronic components than modern technology. An EMP attack may not have impacted some of those components, and those that were destroyed could have been replaced quickly.

In the twenty-first century, computers, phones, and other electronic devices are far more prevalent. Most of the developed world's infrastructure is run by computers with highly sensitive electronic components. A nuclear explosion detonated about thirty to five hundred miles in the upper atmosphere could cause an EMP that would travel along the lines of Earth's magnetic field and potentially devastate a wide area on the ground.

Since an event of this magnitude has never occurred, scientists are not in agreement on the extent of possible damage from an atmospheric EMP. Worst-case scenarios predict a high-altitude detonation could destroy the electronic capabilities of an entire continent, causing catastrophic food and energy shortages. Repairing the damage and restoring power would take years, in which time civilized society would break down. Others believe the "doomsday" scenario is overblown, and such devastation is unlikely.

The US military has been safeguarding its equipment against pulse attacks for years, but most civilian equipment has not been "hardened" to withstand the effects of an EMP. In the twenty-first century, some energy companies have begun to address the potential problem and started development on pulse-protected systems.

Effects from Solar Activity

The sun is a giant nuclear reactor about ninety-three million miles away from Earth. As the sun churns out immense amounts of energy, storms on its surface occasionally produce solar flares that eject large amounts of charged particles into space. If these particles were to impact Earth, they could cause an EMP that could affect a wide area. An EMP caused by a solar storm differs from that of a nuclear weapon. Damage from a solar event would come from the E3 component of the pulse as the charged particles hit the atoms of the upper atmosphere.

Periods of solar activity run in cycles, with the sun at the peak of its activity about every eleven years. In 1859, a large solar storm hit Earth and caused telegraph systems to go down across the United States and Europe. Scientists say if such a storm were to occur today, its effects would be devastating. Only one large solar storm has influenced Earth in the modern era. That event, in March 1989, knocked out the power grid near Quebec, Canada, for more than twelve hours. In 2012, one of the largest solar storms ever recorded just missed Earth. If it had hit the planet, scientists estimate it would have taken years to recover from the damage.

Bibliography

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