Electromagnetic pulse
Based on Wikipedia: Electromagnetic pulse
The Day the Telegraph Lines Burned
In late August 1859, telegraph operators across Europe and North America witnessed something impossible. Their machines began operating on their own, printing messages with no one sending them, sparking and catching fire, delivering shocks to anyone who touched them. Some operators discovered they could disconnect their batteries entirely and the telegraphs would keep working, powered by some invisible force in the air itself.
What they experienced was the first recorded electromagnetic pulse to damage human technology. A massive solar storm, now called the Carrington Event after the astronomer who documented it, had hurled a wave of energy across ninety-three million miles of space to strike Earth. The aurora borealis appeared as far south as the Caribbean. The night sky glowed so brightly that people in the Rocky Mountains woke up and started making breakfast, convinced dawn had arrived.
The telegraph system, humanity's first electrical network, had just learned a harsh lesson about the vulnerability of technology to bursts of electromagnetic energy.
What Exactly Is an Electromagnetic Pulse?
An electromagnetic pulse—often abbreviated as EMP—is simply a sudden burst of electromagnetic energy. Think of it as an invisible flash of electrical force that spreads outward from its source, interacting with anything conductive in its path.
The word "pulse" is key here. Unlike the steady hum of your household electricity or the continuous signal from a radio station, an EMP is brief and violent. It rises to its peak almost instantaneously, then fades away. That sudden spike is precisely what makes it dangerous. Electronic systems expect gradual changes they can handle. They don't expect to be punched.
EMPs can take several forms. Some travel through the air as electromagnetic radiation, the same basic phenomenon as radio waves or visible light, just in a sudden violent burst rather than a steady signal. Others travel through wires and cables as conducted current, racing through electrical systems like a flood through pipes. The energy can manifest as an electric field, pushing and pulling on electric charges, or as a magnetic field, affecting anything magnetically sensitive.
What's fascinating is that according to Maxwell's equations—the fundamental laws governing electromagnetism—you can never have one without the other. A pulse of electrical energy always brings a pulse of magnetic energy along for the ride. They're inseparable dance partners, two aspects of the same phenomenon.
The Anatomy of a Pulse
If you could see an electromagnetic pulse in slow motion, you'd notice its distinctive shape. Most pulses have a sharp leading edge, rising from nothing to their maximum intensity in mere nanoseconds—billionths of a second. Then they decay more slowly, trailing off like the long tail of a comet.
Engineers call this a "double-exponential curve." The pulse climbs exponentially fast, peaks, then falls exponentially slow. The whole event might last only microseconds, but in electronic terms, that's plenty of time to cause havoc.
The speed of that rise matters enormously. A gradual increase in voltage gives circuits time to respond and protect themselves. A near-instantaneous spike bypasses all those defenses. It's the difference between slowly stepping into a cold pool and being thrown in.
EMPs also contain energy across a wide range of frequencies simultaneously. Engineers sometimes describe this spectrum as "DC to daylight"—from the very lowest frequencies, approaching zero, all the way up to just below visible light. This broad spectrum is another reason EMPs are so troublesome. A device designed to filter out one frequency might be completely vulnerable to another.
Nature's Lightning Show
The most common natural EMP is one you've probably witnessed: lightning.
A lightning bolt is essentially a massive electrostatic discharge. Millions of amps of current flow in a fraction of a second, creating an intense electromagnetic pulse that radiates outward from the bolt. This is why your radio crackles during a thunderstorm and why sensitive electronics can be fried by a nearby strike even without being hit directly.
Lightning strikes follow a curious pattern. Before the main bolt, a faint "leader" of lower energy reaches down from the cloud, ionizing a path through the air. Then the main discharge blasts through that prepared channel. Often, several smaller pulses follow the main strike, traveling the same path. All of this happens so fast that to human eyes it appears as a single flash.
Static electricity produces smaller versions of the same phenomenon. When you shuffle across a carpet and touch a doorknob, that tiny spark is an electrostatic discharge—a miniature EMP. In everyday life, it's just an annoyance. But in the wrong environment, it can be catastrophic.
Consider aircraft refueling. The fuel flowing through the hose creates static charge through friction. The aircraft itself may have accumulated charge while flying through the atmosphere. If a spark jumps between the fuel nozzle and the aircraft at the wrong moment, the fuel vapors can ignite. This is why every aircraft refueling operation begins with grounding: connecting the fuel nozzle to the aircraft with a wire so any charge can flow away harmlessly before fuel starts flowing.
The Invisible Threat from Space
Our sun, for all its life-giving warmth, occasionally throws tantrums.
A coronal mass ejection—sometimes called a solar EMP—occurs when the sun ejects a massive bubble of plasma and magnetic field into space. If Earth happens to be in the path of this billion-ton cloud of charged particles, the results can range from spectacular auroras to damaged satellites to potentially catastrophic effects on electrical infrastructure.
The Carrington Event of 1859 remains the most powerful solar storm in recorded history. A similar event in 1989 knocked out Quebec's power grid for nine hours, leaving six million people in the dark. In 2012, a Carrington-class storm missed Earth by about a week—had our planet been slightly further along in its orbit, the results could have been devastating to our now vastly more electrified civilization.
Scientists estimate that a Carrington-scale event has roughly a 12 percent chance of hitting Earth each decade. It's not a matter of if, but when. The question is whether our power grids and electronic infrastructure will be ready.
The Everyday Pulse Generators
You're surrounded by devices creating small electromagnetic pulses right now.
Every time an electrical circuit switches—turns on or off, opens or closes—it creates a tiny EMP. The light switch on your wall, the relay in your car, the millions of transistors in the phone in your pocket: all of them are constantly generating pulses.
In most cases, these pulses are harmless. They're low-energy, and nearby devices are designed to ignore such minor interference. But they can cause problems. In the mid-twentieth century, the ignition systems of gasoline engines were notorious for interfering with radio and television reception. Every time a spark plug fired, it created a pulse that would show up as a crackle on the radio or a stripe across the TV screen. Modern vehicles must meet strict standards for electromagnetic interference precisely because of these effects.
Electric motors present a particular challenge. As the rotating armature passes its internal contacts, making and breaking electrical connections many times per second, it creates a continuous train of pulses. This is one reason why power tools and vacuum cleaners can sometimes interfere with nearby electronics.
The computer you're using contains billions of transistors, each switching on and off billions of times per second. Individually, each switching event creates a tiny pulse. Collectively, they produce a constant hum of electromagnetic interference. This is why computers come in metal cases: the metal acts as a shield, containing most of that electromagnetic noise.
Nuclear Weapons and the Ultimate EMP
In 1962, the United States detonated a nuclear weapon called Starfish Prime 250 miles above the Pacific Ocean. The test was designed to study the effects of nuclear explosions in space. What happened next surprised everyone.
Nine hundred miles away in Hawaii, street lights went out. Burglar alarms started ringing. Telephone service was disrupted. A radio station went off the air. The nuclear explosion had generated an electromagnetic pulse far more powerful and far-reaching than anyone had predicted.
Nuclear weapons produce EMPs through an interesting chain of effects. The initial detonation releases an intense burst of gamma rays—the most energetic form of electromagnetic radiation. These gamma rays ionize the surrounding air, stripping electrons from atoms. Those energetic free electrons interact with Earth's magnetic field and spiral along its field lines, creating a powerful electromagnetic pulse in the process.
A nuclear weapon detonated at high altitude—the military calls this a High-Altitude Electromagnetic Pulse, or HEMP—is particularly devastating. The explosion occurs in the thin upper atmosphere where the gamma rays can travel farther before being absorbed, and where the energetic electrons can spiral more freely along magnetic field lines. A single warhead detonated at the right altitude could potentially affect an entire continent.
The pulse from a high-altitude nuclear detonation arrives in three phases. The first, called E1, arrives in nanoseconds and can damage unprotected electronics directly. The second, E2, is similar to lightning and lasts for microseconds. The third, E3, can last for seconds to minutes and can induce currents in long power lines, potentially damaging transformers and collapsing power grids.
Weapons Without Fallout
The devastating potential of electromagnetic pulses has not escaped military planners.
While nuclear EMP weapons remain in the arsenals of nuclear-armed states, a different category of weapon has emerged: the non-nuclear electromagnetic pulse device, or NNEMP. These weapons generate powerful EMPs through conventional means, without the radioactive fallout and political implications of nuclear weapons.
The concept dates back surprisingly far. In 1951, Soviet physicist Andrei Sakharov—who would later become famous as a nuclear weapons designer turned peace activist—conceived of the explosively pumped flux compression generator. This device uses conventional explosives to rapidly compress a magnetic field, converting the explosive energy into an intense electromagnetic pulse.
Nations kept this research classified for decades, each believing they had discovered something unique. Only gradually did they realize that similar ideas had emerged independently around the world.
Modern non-nuclear EMP weapons take various forms. Some use banks of capacitors discharged into antennas. Others use specialized microwave generators. The United States has tested a cruise missile called CHAMP—Counter-electronics High Power Microwave Advanced Missile Project—designed to fly over enemy territory and disable electronics with directed microwave pulses.
These weapons have significant limitations compared to nuclear EMP. They produce roughly one-millionth the energy of a nuclear weapon of similar weight. Their range is measured in meters or at best kilometers, not hundreds of miles. But they also offer something nuclear weapons cannot: precision. A non-nuclear EMP device can disable a specific building's electronics without affecting the neighborhood, let alone triggering a nuclear conflict.
The Vulnerability of Modern Life
Consider for a moment how much of modern civilization runs on electronics.
Your car contains dozens of microprocessors controlling everything from the engine to the brakes. The power grid is managed by computerized control systems. Water treatment plants, hospitals, air traffic control, financial systems, telecommunications: all depend on electronics that could be damaged or destroyed by a sufficiently powerful EMP.
This vulnerability has grown dramatically over the past few decades. The miniaturization that has made electronics so powerful has also made them more sensitive. A transistor a few nanometers across can be destroyed by voltages that would barely register to older, larger components. The integrated circuits in modern devices contain billions of these tiny components, each one a potential point of failure.
Hard drives store data magnetically, making them potentially vulnerable to the intense magnetic fields of an EMP. Most are shielded by their metal casings, but no shield is perfect. Some data destruction companies actually use controlled EMPs to wipe hard drives before recycling—a legitimate use of the same principle that makes EMPs so threatening.
The physical effects of very large EMPs shouldn't be overlooked either. A powerful enough pulse can heat conductors, start fires, and even physically damage structures. Lightning demonstrates this regularly, splitting trees and blowing holes in buildings.
Protecting Against the Invisible Threat
The good news is that protection against EMPs is possible. The bad news is that it's expensive and requires forethought.
The fundamental principle of EMP protection is the Faraday cage, named after the nineteenth-century physicist Michael Faraday. A Faraday cage is simply a continuous conductive enclosure that redirects electromagnetic energy around its contents rather than through them. Your microwave oven is actually a Faraday cage in reverse: its metal walls keep electromagnetic energy in rather than out.
Critical military and government systems are routinely hardened against EMP. Cables are shielded, buildings are enclosed in metal mesh, sensitive electronics are housed in protective containers. The Pentagon, for instance, is designed to continue functioning through a nuclear EMP attack.
For civilian infrastructure, the picture is more mixed. Some power grid components have built-in protection against lightning-induced surges. Few are designed to withstand a nuclear EMP. The cost of upgrading the entire grid would be enormous, and the probability of any given attack seems low enough that the investment is hard to justify—until the attack happens.
Testing is a crucial part of EMP defense. Specialized simulators recreate the effects of various EMP threats, allowing engineers to identify vulnerabilities before they can be exploited. The largest of these simulators can test entire aircraft or ships. One famous facility, ATLAS-I at Sandia National Laboratories in New Mexico, was a massive wooden structure designed to minimize electromagnetic interference with its tests—a kind of temple to the science of the invisible pulse.
Living with the Pulse
Electromagnetic pulses, natural and artificial, are part of the world we've built. Every lightning storm reminds us that nature commands forces we can only partially control. Every solar cycle carries the possibility of a Carrington-scale event. Every advancement in electronic miniaturization makes our devices more capable and more vulnerable.
The challenge isn't to eliminate EMPs—that's impossible. The challenge is to build systems resilient enough to survive them. This means redundancy: backup systems that can take over when primary systems fail. It means hardening: protecting critical infrastructure against the pulses we know are coming. It means preparation: having plans in place for when, not if, a major EMP event disrupts our electronic world.
The telegraph operators of 1859 were shocked—literally—by forces they didn't understand. We understand those forces now. The question is whether we'll use that understanding to prepare, or whether we'll be caught as off guard as they were, watching in amazement as our machines come alive and then go dark.