EMP, Debunked: The Jolt That Could Fry The Cloud
An electromagnetic pulse (EMP) from the sun or a high-altitude nuclear blast could change life as we know it, but how worried should you really be? Here's a primer.
![](https://eu-images.contentstack.com/v3/assets/blt69509c9116440be8/blteba686947394ead3/64cb57dd383e0e1c6b4824a2/Magnificent_CME.jpg?width=700&auto=webp&quality=80&disable=upscale)
In July, NASA confirmed that a "Carrington Event Class" coronal mass ejection (CME) had occurred on the sun in July 2012. A billion tons of highly charged solar atmosphere had erupted off the face of the Sun and out into space at millions of miles per hour. Luckily, the center of that mighty solar belch crossed Earth's orbit well behind us. If that Carrington Class CME had occurred one week earlier, it would have struck the Earth like its namesake in 1859.
Back then, the telegraph was just a few years old, and the telegraph operators -- the only people really affected -- didn't total even 1% of 1% of the workforce. They put out the fire, fixed the gear as best they could, and were back up and running within two weeks. As recently as 1989, when a much smaller CME took down Hydro Quebec and turned off the electricity in the province for most of a week, people came to work during daylight hours and caught up on typing and filing.
How about now, in the era of the cloud?
Imagine yourself with no power and no communications links for weeks or months. Even if your emergency backup power gets your computers running, you can't access remote data and cloud applications. Your smartphone is a paperweight. People in your organization can't work together, or work at all. Your bank can't tell you how much money you have and, anyway, where would you spend it? The inventory in many stores is another process that's been moved to the cloud. In the second week of the crisis, you get snail mail from your employer telling you not to come into work until the network starts working again.
Terrified yet? Well, calm down. Our cloud-crazy culture could indeed take a jolt, but probably not as big a one as these scenarios suggest.
Since the NASA story came out in the summer news slump, the gee-whiz cohort of science reporters and headline writers had a fine old time scaring people with tales of a CME-caused electromagnetic pulse (EMP) that would fry all modern technology, plunging us back to the nineteenth century, or maybe the ninth. Pop science reporting conjured visions of cellphones up in flames, plummeting airliners, patients electrocuted by their pacemakers, and the total collapse of modern civilization.
Absent from the reporting: In a week, the Earth travels about 45 times the Earth-Moon distance. Reporting that the July 2012 CME missed Earth by 45 times as far as the moon is not quite so dramatic.
While we're at it, EMP has less effect on shorter wires -- in microcircuitry, by definition, wires are very short. EMP is greatly diminished inside cars or steel-framed buildings or underground. It self-cancels in the increasingly common coaxial cables, and doesn't touch fiber optics at all.
But though EMP damage is not the end of the world, it's still a genuine risk today -- and not just from CMEs. Natural and manmade EMPs have done real, serious damage and potentially could do much worse. The perils, the probabilities, and the precautions, like EMPs themselves, come in many sizes from many causes.
Though the July 2012 CME was overhyped, there are real EMP risks to consider. You'll be better prepared if you understand the real odds of the real dangers. Therefore, so that you and your team can be only as scared as you actually need to be, here's a little primer on EMPs.
(Image: NASA Goddard Space Flight Center via Wikipedia)
What is an electromagnetic pulse (EMP), and how does it happen?
It's right there in the name: an energetic interaction of electricity and magnetism (electromagnetic) for a brief time (a pulse). A changing magnetic field induces an electric current in a conductor. Similarly, moving electric charge induces a magnetic field. This can happen one of several ways, and each of those ways can create an electromagnetic pulse:
1. A large charge builds up in a conductor, and it's isolated from a differently charged conductor by an insulator. Then something changes that insulator to a conductor very suddenly, and a massive current surges back and forth until charges equalize. (That's what lightning is; big charges separate until the air breaks down between them.)
2. A magnet or a highly charged object moves very fast. (This is the process that underlies generators and thunderstorms: rapidly spinning magnets or swift-rising highly charged clouds).
3. The direction of current in a long wire changes rapidly (e.g. radio and alternating current transformers).
4. Compression of a coil electromagnet causes an abrupt change in the magnetic flux.
If the charge or the field is very big, or or moves very quickly, or both, the resulting electromagnetic pulse induces unwanted and unplanned -- for voltages in circuits, or if strong enough -- magnetization or demagnetization in storage media and sensors.
The power of an EMP to damage your facility varies with:
-- How much energy went into making it,
-- How far away from you it was made,
-- How much time the process took,
-- The physical size of the conductor where the pulse formed
-- The length of the conductor that delivers the actual voltage to your facility.
In general, low energy, far away, long intervals, and short conductors are good things for avoiding EMP.
The most common measure of EMP from geomagnetic storms is Dst, which stands for "Disturbance -- storm time," and is most commonly measured in nanotesla (nT) per minute.
That unit sounds weirdly tiny. If you were doing a lab experiment and applied a Dst of one nT, taking a full minute to do it, a copper loop a meter in diameter would only produce a 60 billionth of a volt. The needle in your compass is deflected by around 40,000 nT; the magnetic catch on your medicine cabinet exerts millions of nT.
But nT/min is much bigger than it sounds, because it adds up over distances, and in an EMP magnetic fields change in time frames much smaller than a second -- literally as fast as lightning.
It matters, too, over how much area the Dst occurs; a very high Dst in a small area is a completely different matter from a low Dst in a wide area.
By way of perspective:
Dst(nT/min) | EMP sources | Area affected | Notable effects |
---|---|---|---|
Hundreds, low thousands | Geomagnetic storms from solar flares or CMEs | Continental or larger | Dangerous overvoltages, transformer burnouts, massive surges |
High thousands, ten thousands | Lightning at about 1 km distance | Highly local | Surges, blown fuses, damage to connected electrical equipment |
Hundred thousands | Lightning at about 200 m | Highly local | Computer crashes (possibly permanent damage), blown up power transformers, power outages in parts of city. Fires around electrical equipment. |
Millions and tens of millions | Nuclear EMPs at high altitude, nuclear EMPs from close-by small nuclear weapons, lightning within a few meters | Varies | Permanent damage to microelectronics, some erasure and corruption of magnetic media |
Hundreds of millions and up | Conventional EMP weapons | Very small | Disabled vehicles including operating aircraft; numerous small fires, and arcing wherever there's metal |
What it is: Solar weather suddenly produces big charges in the upper atmosphere and renders it highly conductive; immense currents flow through the ionosphere.
Scope: Planet wide or continent wide
Possible Strength: Perhaps 3,000 nT/min, according to an OECD "worst case scenario" study.
Actual observed strength: The Carrington Event has been estimated at 1,760 nT/min. If the July 2012 "near miss" had hit, NASA is guessing around 1,200 nT/min.
In March 1989, a CME about one-third to one-half the size of the Carrington Event triggered a geomagnetic storm over the northern hemisphere with a Dst of around 400-500 nT/min for 92 seconds. Hydro Quebec's high-tension lines were, in places, 1,200-km long, i.e., 1.2 million meters. The long lines acted like one big series circuit, and the result was severe damage to transformers and switching equipment, with protective relays taking down most of the Quebec power grid (and parts of the northeast US with it).
Dangers: Massive voltage surges in long conductors, most especially power and any remaining non-fiber optic, non-coaxial communication cables. Damage to high-voltage transformers might take years to repair and replace.
EMP process: The CME itself is just the trigger for the geomagnetic storm that causes the EMP. In normal conditions, solar electrons and protons constantly enter Earth's magnetic field, which sweeps them toward the north and south magnetic poles. As they enter the Earth's ionosphere, each charged particle rips past millions of atoms, tearing electrons off them and converting them to charged ions. That's how the ionosphere stays ionized even though the charges are constantly finding each other and canceling each other out.
When anything drastically increases the charges in the ionosphere -- such as the trillion-fold increase in incoming charged solar particles that is a direct hit from a big CME -- the ordinary diffusion process is overwhelmed. Huge electric currents flow through the ionosphere, creating a rapidly changing magnetic field, which in turn induces currents in conductors on the ground, 30 to 100 miles below.
What are the chances? A few per century.
Protection: Filter your power, and if you hear we're about to take a Carrington-class hit, unplug and power down. The conductors in a typical office or industrial facility are not long enough to build up significant voltages in Carrington conditions, but you don't want to be hooked up to a 1,000-mile long wire that could.
What it is: Gamma rays from a high-altitude nuclear explosion, via a process called Compton scattering, knock loose enormous numbers of electrons in the ionosphere.
Scope: About a continent; at least 5,000-km radius.
Possible strength: Around 1 million nT/min, which may be the maximum possible from ionospheric events.
Actual observed strength: In 1962, EMP was fashionable and all the big militaries wanted in on it. Soviet Test 184 fired off about a 300-kiloton bomb about 300 kilometers up; the US Starfish Test fired off a 1.4-megaton bomb at about 400 kilometers. Both produced extensive, measurable effects in areas about 5,000 kilometers across, and interestingly ground measurements corresponded to about 1 million nT/min in both tests. This has led to speculation that you can only get so much energy out of an ionosphere.
Dangers: Massive voltage surges in long conductors, big enough to start fires in many locations. Destruction/fires in high-voltage transformers that take years to repair and replace. Some thermal damage to active computer systems, and massive system crashes; unplugged computers inside metal boxes should be all right. Some vehicles likely to stop operating from damage to electronic systems. Field strength might be just barely enough to wipe or corrupt magnetic storage. Smaller devices probably less affected than large ones.
EMP process: Prompt gamma and x-rays from the nuclear explosion spray the ionosphere. Compton scattering causes electrons to be torn off atoms, both creating massive charges and rendering the ionosphere conductive. The number of charged particles produced is several orders of magnitude greater than what happens in a CME, and consequently the ionospheric currents are much larger.
What are the chances? Much lower now that the Cold War is over. But nuclear powers might still prefer to cripple rather than kill each other. It has been argued that if a terrorist group procures a nuclear weapon and a simple Scud-type missile, this sort of attack might represent their best possible "bang for their buck." And targeting an altitude over a whole country is a lot easier than precisely aiming a missile into a possibly well-defended city.
Protection: Surge protectors, fuses, circuit breakers, everything you can do to cut you off from grid power ASAP. Disconnect and turn off everything you can if you know one of these is coming. The first days afterward may require on-ground security personnel because mass media will be disabled and there may be large numbers of fires; the potential for extreme civil disorder is there.
What it is: Small tactical or battlefield nuclear weapons have a significant EMP yield. If you're shielded so that you survive blast and heat, you may find some of your electronics are badly damaged.
Scope: Local
Possible strength: Up to 2 million nT/min, according to Department of Defense studies.
Actual observed strength: About 1.5 million nT/min, half a kilometer from a 24-kT blast.
Dangers: Damage to small electronics, computers, vehicles, and backup power supplies in hardened shelters that successfully rode out the blast and fire.
EMP process: That hard gamma that comes out of a nuclear explosion ionizes the air nearby through Compton scattering, and, for a brief period, the white-hot plasma near the explosion conducts electricity, and large charges flow back and forth.
What are the chances? During the more than 50 years when tactical nuclear weapons have existed, no one has used them. And unless you are a defense facility or located improbably near one, you are unlikely to be targeted. Furthermore, the EMP damage is apt to be a very small matter compared with the much greater damage from blast and fire.
Protection: Don't be where they set off atom bombs. (This is good advice in general.) Hardened facilities should include internal Faraday shielding against EMP.
What it is: The arsenals of at least some of the major military powers include, or soon will, devices for turning the energy from a conventional explosive (like TNT) into EMP, generating very strong localized fields.
Scope: One large building or a small complex at most.
Possible strength: Up to 200 billion nT/min, according to people familiar with the research.
Actual observed strength: It's widely believed that the US, Israel, and perhaps Russia have used these gadgets as an occasional supplement to covert operations, and that China and the EU have them in development. Essentially they knock out virtually everything electronic within a city block or so.
Dangers: Erasure of magnetic media. Shut down of virtually all electronics including those that have been turned off; can probably penetrate at least some metal enclosures and some short distance (a few meters) into the Earth.
EMP process: A big bank of capacitors sets up a huge oscillating current in a coil or system of coils. Simultaneously an explosion compresses the coil so that the flux density rises to very high levels almost instantly.
What are the chances? Right now, nil. If they're operational at all, these are the cherished top secret toys of defense establishments. Unless you are operating something that might be targeted by very high-level special forces, for the moment, you're all right.
In the long run, of course, most human-portable weapons enter the global arms market; in a decade or so, conceivably, terrorists might be able to obtain and use them. Their potential, however, is sharply limited by dispersed backup to the cloud or to multiple data centers.
Protection: Virtually none possible, if these exist and are likely to be used against you. But a very small risk so far; you'd have to be a comic book supervillain to really have to worry.
What it is: Surely you've seen lightning before.
Scope: Up to a kilometer or more away, if it strikes a conductor that allows it to reach your facility.
Possible and actual observed strength: There's a very large experiential base with lightning. Within a few meters of the strike point, around 10 million nT/min; at a kilometer away, the strength falls off to about 10 thousand nT/min.
Dangers: Fires, secondary explosions, severe electrical damage including various freakish accidents.
EMP process: Lightning is a huge oscillating current through ionized air between big charges on the ground and in the clouds.
What are the chances? Over time, nearly every local high point on Earth is hit many times by lightning.
Protection: Lightning rods, insurance, prayer. Most of the precautions against lightning are familiar to people everywhere. If nothing else, it proves we can live with EMP if we just get enough practice.
This is the one that is least likely to matter.
What it is: If one of the exploding stars called supernovae goes off in our neighborhood, within a few dozen light years or so its gigantic X-ray and gamma ray output could cause massive Compton scattering in the ionosphere.
Scope: Planet wide
Possible strength: If ionospheric EMPs are really limited to about 1 million nT/min, then that would be the upper limit.
Actual observed strength: Historical evidence (mostly fossil chemistry and ice samples) argues that these types of EMP have happened, probably at a level comparable to the very largest CMEs.
Dangers: Similar to nuclear ionospheric EMPs with one major exception: The gamma bombardment may continue for many months, and because it will do so, it is quite likely to gradually produce a global brown cloud of nitrous oxide that will eliminate most of our ozone, resulting in the death of the whole food chain (beginning with plants and marine life). So even though you might be a bit perturbed when you find your phone, game console, and tablet are not working, you'll probably be much more bothered a few weeks or months later when the famine sets in.
EMP process: Supernovas radiate unimaginably huge amounts of hard gamma and x-rays, which Compton-scatter in the ionosphere.
What are the chances? Of a nearby one, pretty low. Astronomers have scouted the neighborhood thoroughly, and the nearest real prospect for such a supernova is IK Pegasi, which is 150 light years away -- too far to do much more than give us all some celestial fireworks. A reasonable guess is there's nothing to worry about for the next few million years. Still, it's possible that a close-by supernova or hypernova caused the Ordovician Extinction Event -- and if so, the odds are as bad as once in a billion years.
Protection: The same things you would do for CME and nuclear EMPs will work here. You just won't be around to feel proud of your proactiveness for as long.
(Image: Remnants of a 400-year-old supernova, which appeared in the time of Johannes Kepler. NASA composite image)
Editor's note: In his science fiction, John Barnes has destroyed the world more times than he can remember. See his Amazon author's profile for a view of his destructive habits.
This is the one that is least likely to matter.
What it is: If one of the exploding stars called supernovae goes off in our neighborhood, within a few dozen light years or so its gigantic X-ray and gamma ray output could cause massive Compton scattering in the ionosphere.
Scope: Planet wide
Possible strength: If ionospheric EMPs are really limited to about 1 million nT/min, then that would be the upper limit.
Actual observed strength: Historical evidence (mostly fossil chemistry and ice samples) argues that these types of EMP have happened, probably at a level comparable to the very largest CMEs.
Dangers: Similar to nuclear ionospheric EMPs with one major exception: The gamma bombardment may continue for many months, and because it will do so, it is quite likely to gradually produce a global brown cloud of nitrous oxide that will eliminate most of our ozone, resulting in the death of the whole food chain (beginning with plants and marine life). So even though you might be a bit perturbed when you find your phone, game console, and tablet are not working, you'll probably be much more bothered a few weeks or months later when the famine sets in.
EMP process: Supernovas radiate unimaginably huge amounts of hard gamma and x-rays, which Compton-scatter in the ionosphere.
What are the chances? Of a nearby one, pretty low. Astronomers have scouted the neighborhood thoroughly, and the nearest real prospect for such a supernova is IK Pegasi, which is 150 light years away -- too far to do much more than give us all some celestial fireworks. A reasonable guess is there's nothing to worry about for the next few million years. Still, it's possible that a close-by supernova or hypernova caused the Ordovician Extinction Event -- and if so, the odds are as bad as once in a billion years.
Protection: The same things you would do for CME and nuclear EMPs will work here. You just won't be around to feel proud of your proactiveness for as long.
(Image: Remnants of a 400-year-old supernova, which appeared in the time of Johannes Kepler. NASA composite image)
Editor's note: In his science fiction, John Barnes has destroyed the world more times than he can remember. See his Amazon author's profile for a view of his destructive habits.
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