Is the electromagnetic pulse (EMP) dangerous for humans? How do you defend yourself?

An electromagnetic pulse (EMP) is a very short, violent burst of electromagnetic energy that induces voltages in wires, antennas and circuits many times higher than the ones electronics are built to run on. The strongest one comes from a nuclear explosion high above the Earth, and a powerful solar storm has similar, though slower, effects on power grids. The pulse itself does not harm people directly, but in an instant it can fry electronics, knock out communications and cut the power over an area larger than several countries.

Did you know that the world we live in and know could be wiped out by a single, sufficiently powerful electromagnetic pulse? In this article you will find out how that is possible.

Technology is an inseparable part of our lives

Our civilisation has been thousands of years in the making. From ancient times until today, humanity has done a tremendous amount of work. Building on the achievements of previous generations, we have created a whole host of tools and solutions that make our lives easier. Over the last 100 or 200 years, technological progress has accelerated significantly - and it is still accelerating. Sometimes I even get the feeling that it is moving too fast to keep up with.

We are now living through a so-called technological revolution. The whole of so-called Western civilisation rests on advanced technology that controls (and will control more and more) almost every aspect of our lives. We have computers, mobile phones, televisions, cars, GPS devices, fridges and a whole host of other things without which we cannot imagine normal life.

Modern technology gives us comfort and safety, but unfortunately it is not without weak points. The whole structure of modern civilisation, on which we all depend to a greater or lesser extent, is built like a pyramid, and at the very top sits - electricity. Without it, practically overnight, we lose all the achievements of technology, and our way of life - if we survive - will have to change completely.

I also cover a very similar subject in the article Are we facing blackouts in Poland? How to survive without electricity?

What if… ?

Try asking yourself: what would happen if the electricity were switched off today and not switched back on for days, weeks, months or maybe even years? Would you cope? Where would you get drinking water? How and where would you store food? How would you contact your loved ones, or call for help if you needed it?

If you think a power cut over a large area is unlikely, I’m afraid I have bad news: it is not only possible, it has already happened, including in Europe (on 28 April 2025 the power went out across almost all of Spain and Portugal). One of the most dangerous scenarios is a so-called electromagnetic pulse, also known as an EMP (ElectroMagnetic Pulse).

What is an EMP and where does it come from?

An EMP is a short pulse of electromagnetic energy that can be caused by a natural phenomenon or by humans. Depending on the source, it can take the form of an electric field, a magnetic field, electromagnetic radiation or an electric current flowing through wires.

We come across electromagnetic pulses of various kinds every day. They are produced, for example, by lightning and by various other forms of electrostatic discharge. Electromagnetic pulses are also generated by electric motors and by the ignition systems of combustion engines.

At first glance, then, it looks as though electromagnetic pulses are everywhere and pose no danger to us. That is only partly true, because some electromagnetic pulses are enormously powerful and can destroy electronic and electrical equipment as well as the infrastructure of the power transmission grid.

In this article I would like to focus on the two most dangerous sources of an electromagnetic pulse.

Electromagnetic pulse (EMP) caused by a nuclear explosion (Nuclear ElectroMagnetic Pulse, NEMP)

A nuclear explosion produces three types of electromagnetic pulse, which follow one after another:

E1 - The E1 electromagnetic pulse is a very fast EMP produced during a nuclear explosion. E1 is a brief but intense electromagnetic field that induces high voltages in electrical conductors. E1 is responsible for damage to electronic and electrical equipment, because it pushes the voltage past the electrical breakdown point. E1 can destroy computers and communications equipment, and it rises too quickly (in nanoseconds) for ordinary surge protectors to react in time. Fast-acting surge protectors (such as those using varistors or TVS diodes) cope with it noticeably better, but even they let part of the pulse peak through (more on this in the part about protection).

E2 - The E2 electromagnetic pulse is an intermediate pulse that lasts from about one microsecond to one second after the explosion. E2 has a lot in common with lightning, although an E2 pulse caused by lightning can be much stronger than one caused by a nuclear explosion. Because of these similarities and the widespread use of lightning protection technology, E2 is generally considered the easiest to deal with. However, according to the United States EMP Commission, the main problem with E2 is that it comes immediately after E1, which may already have damaged the devices that would normally protect against E2.

E3 - The E3 electromagnetic pulse is different from E1 and E2. E3 is a much slower pulse, lasting from about a second to several minutes. It is caused by the nuclear detonation briefly distorting the magnetic field. The E3 pulse resembles a geomagnetic storm caused by a solar flare. Like a geomagnetic storm, E3 can induce currents in long electrical lines, damaging their components, such as power line transformers. Because of the similarity between geomagnetic storms caused by solar activity and the E3 pulse, it has become common to call solar geomagnetic storms a “solar EMP”. A “solar EMP”, however, contains no E1 or E2 pulses.

According to statements by Russia and China, some types of nuclear weapons (so-called super-EMP weapons) are designed to maximise the effect of the electromagnetic pulse. For military purposes, the most effective way to use a nuclear electromagnetic pulse is to detonate the weapon in the upper layers of the atmosphere. When the explosion happens high in the atmosphere or above it (tens or even hundreds of kilometres above the Earth’s surface), we speak of HEMP, the high-altitude variant of EMP. A burst 400-500 km above the middle of the United States would cover the whole of the continental US.

While such a high altitude is not desirable for an “ordinary” nuclear explosion (because it weakens the blast and heat waves and produces less radioactive fallout), it is a very effective tactic for an electromagnetic pulse attack. It lets the pulse cover a huge area. Of course, the strength of the pulse falls with distance, but even weakened, it can cause serious damage.

There are also smaller, non-nuclear EMP generators, which can be delivered by bombs, missiles (for example the American CHAMP cruise missile, a demonstrator tested in 2012), aircraft, drones or ground vehicles. Their destructive power, however, is many times smaller than that of nuclear explosions. That has its advantages, though: the effective area can be defined more precisely, and the enemy can be hit at chosen points, disabling only the key parts of the infrastructure.

What an EMP does to electronics and what is most at risk

The mechanism is actually quite simple. Every conductor acts as an antenna, whether it is a power cable, an Ethernet cable, a TV aerial or even the tracks on a circuit board. When the pulse passes through them, it induces voltages of hundreds or thousands of volts, while modern electronics run on a few volts. According to a report Metatech prepared for the US energy regulator, at the strongest field assumed for a nuclear pulse (50 kV/m), even a 10-centimetre piece of wire can pick up about 5000 volts. The transistors in a processor are microscopic and packed very densely, so it takes very little energy to damage them. The result can go one of two ways. The device may just freeze and start working again once you switch it back on, or it may be damaged for good.

The longer the wire, the more energy it collects. According to guidelines from the US agency CISA, long overhead lines can see hundreds of thousands or even millions of volts, a power cable at the socket from 1 to 50 thousand volts, and a shielded cable from 1 to 100 volts.

So the things most at risk are everything that hangs on long cables and antennas:

• computers, routers, network switches and other networked equipment (in tests by the US EMP Commission similar equipment started freezing at about 4 kV/m, permanent damage occurred from about 8 kV/m, and more often above 15 kV/m),
• traffic light controllers, which in the same tests started going haywire at just 1-5 kV/m,
• the electronics that run the power grid, waterworks and telecommunications, in other words everything that keeps the electricity in your sockets and the water in your taps,
• devices that are switched on or charging at the moment of the pulse.

The least at risk is small battery-powered equipment, unplugged from any cables and without a long antenna. In the Commission’s tests, handheld and vehicle radios survived a field of 50 kV/m undamaged, and the ones that were switched on at most froze, so all it took was to switch them off and on again. CISA also points out something that is easy to forget. The phone in your pocket stands a good chance of surviving, but what good is that when the mobile network it relies on is much less resilient.

How far does an electromagnetic pulse reach?

That depends above all on what caused it. With a nuclear explosion high above the Earth (according to the EMP Commission’s 2004 report, that means an altitude of about 40-400 km), the pulse reaches everywhere the burst point can be seen from, all the way to the horizon. The higher the explosion, the further away the horizon.

It is easy to work out. The radius of the affected area, measured along the Earth’s surface, is R × arccos(R / (R + h)), where R is the radius of the Earth (about 6371 km) and h is the altitude of the explosion. Roughly, it comes out like this:

• a burst at an altitude of 30 km gives a radius of about 620 km and an area of about 1.2 million km², almost 4 times the size of Poland,
• at 100 km, a radius of about 1120 km and an area of about 3.9 million km², more than 12 times the size of Poland,
• at 400 km, a radius of about 2200 km and an area of about 15 million km²,
• at 500 km, a radius of about 2450 km and an area of about 18.6 million km².

The formula agrees with the Metatech report, which gives a radius of 972.8 km for a burst at an altitude of 75 km, exactly what the calculation gives. That is where the whole of the continental US, mentioned above for a burst at 400-500 km, comes from.

Range, however, is not the same as strength. The field is strongest near the point directly below the burst and gets noticeably weaker towards the edges (in the Metatech example it averages about 1/8 of the maximum). The American Starfish test of 1962 shows this well. The bomb went off about 400 km above Johnston Atoll in the Pacific, and in Hawaii, about 1400 km away, some of the street lighting went out, alarms went off and circuit breakers tripped, and a communications relay station was damaged. Hawaii did not plunge into darkness, though. According to an analysis by the Sandia laboratory, about 30 street light circuits failed on Oahu, roughly 1% of the lamps.

Non-nuclear sources are on a completely different scale. In 2001 a Russian exporter advertised a device working within a radius of 10 km, and the Congressional Research Service report I link to at the end writes about microwave weapons that are effective from a few miles away. That is a matter of kilometres, not hundreds of kilometres. More on these weapons in the next section.

EMP weapons without a nuclear explosion

Do electromagnetic weapons exist? Yes, although not like the ones in films. Instead of an atomic bomb, they use high-power microwave generators (HPM for short), which send short, very strong bursts of radio waves towards the target. They damage electronics in the same way, through voltage induced in wires, but over a small area and usually in one direction. The target is the enemy’s electronics, not people.

Who has them? Most is known about the American programmes. In October 2012 Boeing and the US Air Force Research Laboratory (AFRL) tested the CHAMP missile over a test range in Utah. It flew a pre-programmed route and fired high-power pulses, knocking out the electronics of one target after another. It was a demonstrator, not a weapon in service. The same laboratory built THOR, a microwave system for defending air bases against drone swarms. In 2001 Russia showed the Ranets-E system at an arms fair in Malaysia, advertised as able to disable precision weapons within a radius of 10 km. The catch was that a buyer could get neither a finished device nor its documentation, only pay for further development. That is why I treat it more as an advert than as proof that such a weapon works.

How far do they reach? None of these programmes has an officially published range, and what has been disclosed points to kilometres. The strength of the waves falls quickly with distance, which is why microwave weapons are suited to knocking out a specific target with precision, not a whole country. For that you need a nuclear explosion.

People also often search for how to create an electromagnetic pulse. Weak pulses are produced every day by every spark, every electric motor and every car ignition system (I wrote about this above). A pulse strong enough to destroy electronics takes a nuclear explosion or a high-power military generator, and you won’t find instructions for building anything like that here. This is a blog about how to survive, not about how to wind up your neighbours 😉

The best-known military incident involving an electromagnetic pulse (EMP)

Although it is not entirely clear whether the technology used in the attack was based on EMP or rather on jamming and disrupting the enemy’s radio signals, the message of this case is unmistakable and should give any sensible person food for thought. Even though a lot suggests that the whole story was made up by Russian intelligence, I still think it is worth telling. (I should point out, however, that this story has never been officially confirmed. The Pentagon only spoke of a dozen or so provocative passes by a Russian aircraft over the ship and gave assurances that the ship was never in danger, and the manufacturer of the Khibiny system itself called the whole tale a newspaper hoax. Many media outlets and analysts describe it as an example of Russian propaganda.)

Background

On 10 April 2014, the destroyer USS Donald Cook entered the Black Sea, and on 12 April a Russian Su-24 tactical bomber flew over the ship, triggering an incident which, according to several media reports, completely demoralised its crew, so much so that the Pentagon issued an official protest.

The main character

The USS Donald Cook is a fourth-generation guided-missile destroyer whose key weapons are Tomahawk cruise missiles with a range of about 1600 km (the version with a nuclear warhead and a range of 2500 km was put into storage in 1991 and later retired). The ship has 90 vertical launch cells for all of its missiles, not just the Tomahawks, so it cannot carry as many as 150 of the latter, as some accounts claimed. The American destroyer is also fitted with the latest Aegis combat system. This is an integrated naval weapons system that can link the missile defence systems of all ships connected to the same network, so that they can detect, track and destroy hundreds of targets at the same time.

On top of that, the USS Donald Cook is equipped with 4 large radars whose power is comparable to that of several ground stations. It carries the anti-aircraft missiles for its own protection in the same 90 cells as the Tomahawks.

The antagonist

Meanwhile, the Russian Su-24 that devastated the USS Donald Cook carried neither bombs nor missiles, only a pod mounted under the fuselage which, according to the Russian newspaper Rossiyskaya Gazeta, held a combat device called Khibiny.

The incident

As the Russian jet approached the American ship, Khibiny switched off all the radars, control circuits, systems, data transmission and so on aboard the American destroyer. In other words, the almighty Aegis system was cut off and shut down as easily as you switch off a TV with the remote.

The Russian Su-24 then simulated a missile attack on the USS Donald Cook, which at that moment was literally deaf and blind. As if on an exercise, the Russian aircraft - unarmed - repeated the same manoeuvre 12 times before flying off. Afterwards, the state-of-the-art fourth-generation American destroyer sailed on a port visit (according to the Pentagon) to Constanta in Romania.

The aftermath

Since this incident, which the Western media carefully hid and still hide (I found it very hard to find any information about it, even though the case was quite widely discussed at the time), and despite widespread reassuring reactions and comments from defence industry experts, no American ship has ever come close to Russian territorial waters.

According to some media reports, 27 sailors from the USS Donald Cook asked to be released from active duty. They must have gone through quite a trauma.

Epilogue

Vladimir Balybin - director of the electronic warfare research centre at the Russian Air Force Academy - commented on the event as follows:

“The more complex a radio-electronic system is, the easier it is to disable it with electronic warfare.”

source

Did this story really happen, or is it rather a product of the Russian propaganda machine? It is hard to say, but it is almost certain that events like this are entirely possible.

Coronal mass ejection (CME)

In 1859 something happened that should be a warning and a cautionary tale for us. A powerful solar storm struck, and its effects have gone down in history for good. On 1-2 September that year, a so-called coronal mass ejection hit the Earth’s magnetosphere and caused one of the largest geomagnetic storms ever recorded. The flare in the solar photosphere that preceded it was observed on 1 September, independently of each other, by the British astronomers Richard C. Carrington and Richard Hodgson, which is why in English-language literature the whole phenomenon is known as the Carrington Event.

A solar EMP caused atmospheric anomalies all over the world

While it lasted, auroras were seen all over the world - in the northern hemisphere they reached as far as the Caribbean. The lights over the Rocky Mountains in the United States were so bright that their glow woke up miners, who started making breakfast because they thought it was already morning.

People in the north-eastern United States could read a newspaper by the light of the aurora. The aurora was visible from the poles to places such as south-central Mexico, Queensland, Cuba, Hawaii, southern Japan and China, and even at lower latitudes very close to the equator, for example in Colombia.

Telegraph network infrastructure destroyed

Telegraph systems all over Europe and North America failed, and in some cases their operators got electric shocks. Some telegraph equipment gave off sparks. Some telegraph operators could keep sending and receiving messages even after disconnecting their batteries - the lines were powered by the current induced by the storm.

If a solar storm of that strength happened today, it would cause widespread electrical disruption, blackouts and enormous damage from prolonged power cuts. In May 2013, researchers from Lloyd’s of London and the American company Atmospheric and Environmental Research (AER) used data from the 1859 event to put the present-day cost of a similar event in the United States alone at 0.6-2.6 trillion US dollars!

Geomagnetic storms are nothing new - we have been lucky

Strong solar storms also occurred in 1921 (in some respects that one matched the 1859 storm) and in 1960, causing widespread radio disruption at the time. The geomagnetic storm of March 1989 shut down the entire Hydro-Québec transmission grid in Quebec, Canada, for about 9 hours, leaving the whole of Quebec without power.

On 23 July 2012 a solar storm of similar strength to the one in 1859 was observed, but the cloud of plasma thrown out by the Sun (the CME) missed the Earth, because the eruption came roughly a week too late (!). The most recent very strong geomagnetic storm (the top level, G5, on NOAA’s five-level scale, and the first one since 2003) hit the Earth on 10-13 May 2024. Auroras were visible in Poland too, and the power grids in North America came through it without major failures.

How do you protect yourself and your devices from an electromagnetic pulse (EMP)?

A strong enough electromagnetic pulse can damage a great many electrical devices, but different devices vary widely in how well they withstand it. The most vulnerable are those connected to long cables or an antenna at the moment of the pulse, and the least vulnerable is small battery-powered equipment, disconnected from everything. Interestingly, old electronic vacuum tubes cope with electromagnetic pulses much better than semiconductors. That does not mean, however, that they are completely immune. Modern electronics, on the other hand, such as computers, hard drives and phones, are much more vulnerable to this kind of damage, especially when they are plugged into the mains or charging.

Protect your devices with a Faraday cage

So what can we do to protect our electronics and electrical devices from the destructive force of an electromagnetic pulse? The best protection against such an event, and one that any of us can make on our own, is the so-called Faraday cage, long known to science. I won’t go into the details of how it works here, because they are not that important. Besides, many of us probably still remember it from school.

In practical terms, all you need to remember is that any tightly closed (but not necessarily airtight) metal container is a Faraday cage. It could be, for example, a metal dustbin (with the gaps sealed), a box you keep jewellery in, or a gun safe (what matters is that the lid or door makes metal-to-metal contact all the way round - you can tape over the gap with conductive aluminium tape - and that the equipment inside does not touch the metal walls, so line the inside with cardboard, for example). If you take a close look at the glass door of a microwave oven, you will see a fine mesh on it. That is a Faraday cage too (but don’t store electronics in a microwave - all it takes is for someone to switch it on without realising, and with a battery or metal inside, that could start a fire). You can put electronics and any other equipment you would like to protect from an electromagnetic pulse in a metal container.

How do you make a Faraday cage yourself?

Making a Faraday cage yourself is very simple. All you need is any reasonably sturdy and rigid container - it could be a shoebox or a wooden crate. Wrap it tightly in aluminium foil on every side. Any aluminium foil from your kitchen will do; just make sure it has no holes or gaps. A box or crate tightly wrapped in aluminium foil can give effective protection against an electromagnetic pulse (provided you first wrap the device in something non-conductive, such as paper, so that it does not touch the foil, and apply the foil itself in several overlapping layers with no gaps). If you want to be even more certain, you can double up the whole system. Just put one smaller Faraday cage inside another, larger one.

Faraday Cage: Garbage Can, Really?

The measures above should be enough; just bear in mind that this solution has never been tested in a real disaster, so no one can say with 100% certainty that it will work. Remember that a powerful enough electromagnetic pulse can also damage equipment you rarely think about in this context. That includes a power generator or a portable power station with a solar panel, so if you have one and want to protect it from an electromagnetic pulse, you should shield it in the way described above as well.

One last note on the Faraday cage - some people claim it has to be earthed to work properly, but that is not true: a Faraday cage does not need earthing.

What to keep in a Faraday cage?

The cage doesn’t have to be big. You are not hiding your whole house in it, only the things that will help you get through the first weeks without electricity and find out what is actually going on. Below is my suggestion, and the list is open:

• a battery-powered or wind-up radio and spare batteries, because when the internet and the mobile network go down, the radio may be your only source of news,
• a head torch and an ordinary torch,
• a spare phone, even an old one, with a charger and a cable,
• a power bank and a small solar panel to charge it,
• a USB stick with copies of documents, photos and your loved ones’ phone numbers,
• walkie-talkies, if you have agreed on them with your family.

Take the batteries out of small electronics if you can, because according to CISA they can add to the damage in the circuits. Cables that can’t be detached from a device go in together with it. Some of these things should be in your bug-out bag anyway, and if you are wondering what else to put in it, have a look at my article on the bug-out bag.

How do you test a Faraday cage with a phone?

The simplest test takes a minute. Put a phone that is switched on inside the closed cage and call it from another one. If it rings, the cage is letting waves through and you need to fix the gaps or add another layer of foil. If it doesn’t ring, do the same with a radio tuned to an AM or FM station (CISA also recommends this test, with a phone and a radio).

Just remember that this is a very rough test. A phone only checks the mobile network bands (from a few hundred megahertz to a few gigahertz), and only whether the cage weakens the signal enough to drop the call. According to CISA, the E1 pulse covers frequencies from about 1 MHz to a few hundred MHz, largely lower than the mobile network, so a silent phone is a necessary condition, not proof that the cage will protect your equipment. The same goes for the metal dustbin in the video above. Gaps around the lid, the handles and the bottom can let waves through, which is why CISA considers that a bin without modifications does not give reliable protection. Seal them first, as I described above, and only then test the bin with a phone and a radio.

Protection beyond the Faraday cage

A cage protects the equipment you keep in reserve. But what about the things you use every day? There is no single solution here, but a few simple things noticeably reduce the losses.

First, unplug the cables. Equipment that isn’t connected to the mains, an antenna or an internet cable picks up much less energy. Pull the plugs out at the device itself, not just at the wall socket, because a cable hanging from a computer still works as an antenna. If a cable can’t be detached, don’t stretch it out, coil it up next to the device. Of course, no one is going to warn you about an attack, but the same habit comes in handy in every thunderstorm, and equipment you rarely use can stay unplugged for good.

Second, surge protectors. A surge protection strip and protectors on the antenna and the internet cable are a good thing, but be aware of their limits. Ordinary surge protectors are designed with lightning in mind, while the E1 pulse rises in about one nanosecond, which is much faster. CISA says that with such a fast pulse almost every protector of this kind lets the voltage peak through, often as much as 3 times higher than the level it was supposed to limit it to. Among the cheap options, varistors and TVS diodes cope best, and for charging equipment the agency recommends protectors with a response time of 10 ns or less. Reliable protection only comes from EMP-certified protectors on every wire, but those are solutions for critical infrastructure, not for a flat.

Third, fibre instead of copper. Optical fibre carries light, not electricity, so it doesn’t pick up the pulse the way a copper cable does. The only condition is that there is no metal in the cable (some fibre cables have a metal armour or a metal support wire). Also bear in mind that the fibre modem at home still has to be powered from a socket, so it will need a surge protector too.

Fourth, backup power. A generator that is meant to start after an EMP shouldn’t be permanently connected to your home wiring, because the long power line will carry the pulse into it and can fry its electronics. Keep it disconnected, together with a supply of fuel (CISA talks about a week’s supply). A portable power station with a solar panel is a good addition, provided the panel and the station are kept disconnected, ideally in a cage, as I wrote above.

What setting off an EMP means for people

In most cases, the direct effect of an electromagnetic pulse on a person will not do any lasting harm, unless we happen to be exceptionally unlucky and get struck by lightning. The indirect effects are dangerous, though: without electricity, medical equipment (oxygen concentrators, ventilators, home dialysis machines) and fridges with medicines, such as insulin, will stop working, and on top of that it will be hard to call an ambulance. If someone in your home depends on such equipment or medicines, start your emergency plan with them.

A much bigger problem is surviving without all the conveniences of civilisation. A strong electromagnetic pulse can knock out electricity over a very large area, permanently and for a long time. As I mentioned earlier, our civilisation runs on electricity, and without it all the systems we are used to stop working: not only do we lose communication and contact with the outside world, but getting drinking water also becomes difficult. The pumps that supply water in cities will stop as soon as the power goes (some waterworks have emergency generators, but they need fuel too and can be damaged by the pulse itself), although water will keep flowing from some taps for a while, because part of the infrastructure works by gravity.

Keep a supply of drinking water

That is why the most important thing is a supply of drinking water. Build it up in advance: the Polish government’s Safety Guide (Poradnik bezpieczeństwa, in Polish) recommends at least 3 litres per person per day, for at least 72 hours, which makes 9 litres per person. And when the power goes, fill the bath and every container you have straight away, while the water is still running. It is also a good idea to buy a so-called life straw, which filters water and makes it safe to drink. With it you can drink almost any water without fear of being poisoned, even from a puddle (such filters do not remove viruses or chemicals, though, so be careful). Water from an uncertain source is best boiled as well after filtering.

Apart from drinking water, you need to think about the other things people need to live: food, warmth, medicines - but that is a topic for another article.

Get out of the city

If an electromagnetic pulse were ever set off, people living in big cities would feel it most, so if you live in a large urban area, you should think about some kind of emergency plan and work out how to get out of the city to a safer place. Just bear in mind that public transport running on mains power (trams, trolleybuses, the underground) will stop, and there will be nowhere to charge an electric scooter. Most cars will probably still run (in tests by the US EMP Commission on 37 cars made between 1986 and 2002, the engine cut out in only three of them, and they could be restarted), but without electricity you won’t be able to fill up at a petrol station, and the roads will be jammed with traffic and dead traffic lights. So you may be left with walking, or riding a bike or another muscle-powered vehicle. (Just remember that leaving the city on foot, with no destination and no supplies, especially in winter, can be more dangerous than staying at home. Prepare your escape plan in advance - where to go, which way and where the family will meet - but decide whether to actually leave depending on the season, the health of your household and announcements from the emergency services.)

Which cars will survive an electromagnetic pulse?

The best data on this come from the tests I mentioned above. The EMP Commission put 37 cars made between 1986 and 2002 into a simulator and gradually raised the field strength, up to about 50 kV/m. Cars with the engine switched off suffered no damage at all. The three cars whose engines cut out had been exposed to a field of about 30 kV/m or stronger. In a fourth car the dashboard electronics had to be repaired, 25 cars showed only minor symptoms, such as flashing warning lights, and 8 did not react at all.

Lorries made between 1991 and 2003 fared much the same. Of the 18 tested, the engine cut out in three, two could be restarted straight away, and one went to the garage on a tow truck. The Commission estimates that in a strong field at least about 10% of cars may suffer serious effects, including the engine cutting out, and in about 15% of lorries the engine will cut out. That is more than enough to gridlock a city, especially as traffic lights start going haywire at just a few kV/m.

These results should be taken with a pinch of salt, though. Testing of each car was stopped at the first reaction, so the ones that did react never got the full dose. It is only 37 cars, and from 1986-2002 at that, while today’s cars contain far more electronics. I wouldn’t trust the lists of “EMP-proof cars” that circulate on the internet until I see the tests they are based on. In my opinion, the most sensible thing is to assume that your car will most likely run, so always keep at least half a tank in it, because filling up may be a problem.

Better safe than sorry

A chilling scenario emerges from all of the above. An electromagnetic pulse could cause a total catastrophe on an enormous scale. Even if we are not afraid of a nuclear conflict, our nearest star - the Sun - has the potential to destroy civilisation as we know it in a single, violent pulse. What makes it even more frightening is that such outbursts have already happened in the past, and not so very long ago. Perhaps the next one is only a matter of time.

I do, however, see two different scenarios here. A solar storm as strong as the one in 1859 will certainly happen again, we just don’t know when. Scientists who have tried to calculate it give it anything from less than a 1% chance (Moriña et al., 2019) to about a 10% chance over the next 10 years, depending on the model used (Riley and Love, 2017). I consider a nuclear pulse high above our heads a much less likely scenario, because it requires a decision to use nuclear weapons. If it did happen, though, the effects would be enormous and would come in an instant, over an area many times larger than Poland.

You can find more about the potential damage caused by an EMP in this Congressional Research Service report for the US Congress (2008).

Source of some of the information: I translated and adapted the definition of EMP and its everyday sources, the description of the E1, E2 and E3 pulses and of HEMP (together with the caption of the Trinity explosion photo), and the parts about the Carrington Event and later solar storms from the English Wikipedia articles “Electromagnetic pulse”, “Nuclear electromagnetic pulse” and “Carrington Event” (authors: Wikipedia contributors). The originals are available under the Creative Commons Attribution-ShareAlike 4.0 (CC BY-SA 4.0) licence, and I share my translated and adapted versions of these parts under the same licence.