The Ugly Truth About Electromagnetic Pulse (EMPs) – Part 1, An Introduction

By Dr. Arthur Bradley author of Disaster Preparedness for EMP Attacks and Solar Storms

There is a great deal of confusion about what an electromagnetic pulse (EMP) is and how best to protect against them. This three-part tutorial is meant to help clear up some of this confusion as well as dispel a few myths that frequently circulate the internet. This first part will be a general introduction. The second will discuss building an effective Faraday cage. And the third part will answer questions that I am frequently asked on this topic.

What is an EMP?

An EMP is an intense broadband burst of electromagnetic energy. It can be the result of many things, including lightning, a nuclear explosion, or specialized EMP weaponry. Of all of these sources, the EMP that results from a high-altitude nuclear explosion has the greatest potential to cause widespread damage. When people talk about an “EMP attack,” they are almost always referring to one caused by a high-altitude nuclear detonation. Many times solar events are also described as causing an EMP, but it’s important to understand the differences between the electromagnetic disturbance resulting from the Sun and the other sources mentioned—more on that later.

Tactical Advantages

EMP-generating devices can be employed in conventional, large-scale warfare, but they are more likely to be used as asymmetric weapons by a hostile state or terrorist group that strives to inflict great damage without requiring the need for military supremacy. EMP weapons offer several tactical advantages over conventional weapons, including:

  • Affecting all targets in range without requiring knowledge of the specific electronic systems
  • Being largely independent of weather,
  • Offering a scalable area of attack, ranging from single electronic assemblies using a directed energy weapon, to an entire continent using a high-altitude nuclear detonation,
  • Causing lasting effects through permanent destruction to both civilian and military electronic hardware,
  • Having a damage-to-cost ratio that is much higher than conventional or “dirty bomb” weapons, and
  • Not directly harming humans or animals, making full-scale retaliation politically difficult.

Area Affected

A high-altitude EMP (HEMP) emits gamma rays that strip electrons from atmospheric atoms. There are several unique atomic interactions that occur, including photoelectric absorption, Compton scattering, and pair production, all of which result in the generation of free electrons. Most of this ionization occurs at an altitude of 12 to 25 miles (20 to 40 km) in a region of the atmosphere known as the “Source Region.” These free electrons ultimately interact with the Earth’s magnetic field lines, resulting in an intense electromagnetic pulse that affects the surface. Saturation occurs in the Source Region as it become more and more conductive, limiting the maximum field to 50-100 kV/m – very high fields, indeed!

The area affected by the high-altitude EMP is determined by line of sight and, therefore, largely a function of altitude. The greatest threat is from a high-altitude EMP produced by a nuclear weapon detonated 25 to 250 miles above the Earth’s surface. It is reported that if even a small 1 to 2-megaton nuclear bomb was detonated 250 miles above the central states, the resultant pulse could disrupt, disable, and damage electronics across most, if not all, of the continental United States.

1x1.trans The Ugly Truth About Electromagnetic Pulse (EMPs) – Part 1, An Introduction

Electromagnetic Pulse Effects

Fig. 1: Area affected by high-altitude EMP attack at different detonation heights

Electronic Damage

An EMP damages electronics by inducing voltages and/or currents far above the levels that the circuits were designed to withstand. This leads to overheating or electrical breakdown of components. The energy is coupled into electronic systems by three mechanisms: electrical induction (energy transferred to conducting wires or junctions), magnetic induction (energy transferred into closed conducting loops), and through transfer impedance, such as energy transferred to buried conductors. Most modern integrated circuits are susceptible to high-frequency pulses, whereas large electrical systems, including our commercial power grid, are more susceptible to low-frequency pulses. Unfortunately, an EMP has both high- and low-frequency pulse content. The Sun, however, only causes low-frequency electromagnetic disturbances, which will greatly affect how we protect against those events – coming in Part 2.

An EMP is defined by its timing, field strength, and frequency content. The precise extent of damage that a particular EMP will inflict is not easily predicted because it is dependent on many factors, including field orientation, waveform polarization, circuit geometry, filtering, and shielding. It is often taken that field levels of 10 kilovolts per meter (kV/m) or greater are sufficient to cause widespread damage to electronic systems. Note that the peak fields from a high-altitude EMP would likely be in excess of 50 kV/m.

Devices that are most susceptible to an EMP are those that use solid-state semiconductors, such as computers, alarm systems, radios and transceivers, control systems, and communications equipment. Electronic equipment designed for higher currents, such as transformers, motors, and circuit breakers are less susceptible. Batteries are not susceptible to EMP energy.

Overall Impact

The greatest threat from an EMP is its ability to disrupt, damage, and destroy electronic hardware. Affected systems include the electrical power grid, cellular and wired communications systems, the internet, personal electronics, agricultural systems, airplanes, gasoline pumps, satellites, water purification plants, generators, automobile electronics, and nearly every other type of modern electronic device.

Due to the interdependency of systems, a cascade of failures would likely promulgate through every major infrastructure. It is estimated that a high-altitude EMP attack on the continental U.S. would cause several trillion dollars of damage in cascading failures of interdependent systems. Such a disruption would crush the economy and seriously degrade critical infrastructures, including: electrical power, telecommunications, financial, petroleum and natural gas, transportation, food, water, emergency services, space operations, and government.

Coming soon… EMPs – Part 2, Building a Faraday Cage

If you have comments or questions regarding EMPs, write the author at, consult Disaster Preparedness for EMP Attacks and Solar Storms, or watch my free videos on YouTube (search disasterprepper).

About the Author

Dr. Arthur Bradley is the bestselling author of the Handbook to Practical Disaster Preparedness for the Family, the Prepper’s Instruction Manual, the Disaster Preparedness Handbook, and Disaster Preparedness for EMP Attacks and Solar Storms. He is also the author of the bestselling post-apocalyptic series, The Survivalist. He provides free disaster preparedness information at

Dr. Bradley is an Army veteran, father of four, martial artist, weapons expert, and dedicated homeschooler. He is active in volunteer youth organizations, including the Boy and Girl Scouts of America. He holds a doctorate in engineering and currently works for NASA. Having lived all across the United States, Dr. Bradley writes from personal experience about preparing for a wide variety of disasters. He has been featured in the New York Times, Toronto Sun, Men’s Journal, Costco Connection, Popular Mechanics, and Money magazine.

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  1. Oldalaskan says:

    Read the books “One Second After by William R. Forstchen and the “Going Home” series by A. American.

  2. Dr Bradley, thank u for this article, & I look forward to the sequel. What kind of engineering is your PhD in? & what school is it from?

    • Hi Red,

      The fourth book in the Survivalist series is due out next month. That series has really caught the imagination of people wondering what it might be like to live in a post-apocalyptic world, following a global pandemic. As for my degree, I have a Ph.D. in electrical engineering from Auburn University. I work at NASA as my day job.

      Best wishes, Arthur

  3. Lake Lili says:

    Dr. Bradley, Thank you for your article. I can see from the illustration the you gave that even at a height of 300 miles, which would affect all of the US and all primary Canadian cities would not reach Nova Scotia, Newfoundland or Labrador. In your estimation could they shut off the switches to the Quebec grid at Labrador’s Churchill Falls power dam fast enough to prevent the Atlantic Region of Canada from going down? In which case, theoretically could Canada’s Atlantic region still be functional? Thanks.

  4. It’s ironic that much of Canada’s network has proven more susceptible to solar events, but as you said, just outside the expected range of a single EMP detonated over the central states. The truth is I don’t know the answer to your question, but I doubt it that Canada would fully escape without damage. While the radiated effects of an EMP might be minimal in Canada from an attack like this, I suspect energy would travel very quickly over the conducted channels, causing some damage to their infrastructure as well. Also, if multiple warheads were detonated, both the area affected and overall damage could be greatly enhanced. With all that said, if the US is the target, Canada would almost certainly be in better shape when the dust has settled.

  5. JP in MT says:

    Finally, time to start the EMP book!

    This is a possibility that concerns me the most, as preparing for it is so specialize, costly, and has a great many unknowns.


  6. Baby catcher says:

    Hi. I’m no rocket scientist, but was curious as to how high 300 miles is in the atmosphere. Is it even possible for a delivery system to go that high while still being under control of the operators, or is that altitude considered outer space? Thanks, and great article….I didn’t know if anyone besides Russia and the US had that capability…

    • Three hundred miles is all the way up to the thermosphere. To give you an idea, this is the same region at which the space shuttle (when we had one) orbited. There are certainly delivery systems that can get up this high, and as you suggested, they were mostly in the hands of the big three (US, Russia, and China). Israel, France, India, and even North Korea are also considered to have some intercontinental missile capability, but I’m not certain which have been demonstrated to reach these kinds of altitudes. Terrorist attacks would likely be at a lower altitude, perhaps launched from the Gulf of Mexico. An EMP detonated over the Eastern Seaboard (a likely target) would cause untold financial damage to our nation.

  7. Mary Beierle says:

    With Iran and Russia now cruising the Atlantic Ocean and the Gulf of Mexico, along with the Chinese working eagerly in Mexico and controlling the Panama Canal, I fear that we are closer than ever to an EMP attack on our country. From those points in the oceans it would be easy to fire a nuclear tipped missile (or several) into the atmosphere practically anywhere in our America. Our three electric grids are not hardened to attack because our politicians would rather spend the money protecting a smelt than protecting the people. Arthur, I have all your books and they are enlightening. I would also recommend Michael Maloof’s book, “A Nation Forsaken” which relates his efforts to have Congress harden the grid and what would happen in an EMP attack. Scary.

  8. patientmomma says:

    I noted in your article that batteries are not affected by EMPs. Two of my family members have implanted pacemakers and ACIDs to control their heart rhythms, so is it safe to assume their devices would not be harmed by EMP?

    • Unfortunately, no, I wouldn’t assume this at all. While the batteries themselves would be immune, the control circuitry would not. Small devices like this have microelectronics, which have been shown to be susceptible to electromagnetic energy. What I don’t know is if there is any kind of high-frequency filtering, shielding, or other mitigation techniques used to make them less susceptible. The manufacturer should be able to provide that type of information.

  9. Buckwheat says:

    Thank you for this. I am currently working on this scenario. I figure if this is the worst to expect, everything else will be cake (relatively speaking).

    I think that it would be really interesting for you and Joel Skousen to contribute a joint article. According to Skousen, this is the scenario that Russia/China are planning to unleash on us.

    • An EMP is certainly “on the table” by Russia, as they have made that very clear on a couple of different occasions. The Chinese also have the capability to conduct this form of attack. The biggest question in my mind is under what conditions would they risk such an action. It would almost certainly result in global war, one in which everyone would lose to one degree or another.

  10. An electromagnetic wave is also a radio wave. As such an even simpler way to describe it is as a high energy pulse of radio waves.

    You obviously know your stuff and your article is remarkably free of the misinformation I see in many other articles on this topic. That said, I would like to add a couple of clarifications.

    The Compton effect is gamma rays hitting electrons and causing them to move at near relativistic speeds until they recombine with another nucleus. As such the amount of energy in the EMP is a function of the amount of gamma rays emitted by the nuclear weapon. The 1 to 2 Megaton weapon cited can only be a hydrogen bomb as no uranium or plutonium bomb can be built with that yield size. Per my notes, the weapon in the Starfish Prime test was a 1.4 Megaton weapon which yielded 0.1% of its energy in gamma rays, of which 95% were absorbed by the casing. In contrast, a uranium bomb of the type built by Pakistan and being developed by Iran and North Korea will yield about 20 Kilotons, but 0.5% to 3.5% of that will be in gamma rays and as there is almost no casing, there will be almost no absorption. As such the weapons held by those most likely to use them against the US will do almost as much damage as the larger weapons.

    The damage from EMP is line of sight and the higher a weapon is exploded, the greater the area that can be seen line of sight. However, the basic law of physics is that energy can neither be created or destroyed, only changed in form. The result of this is that the amount of destructive energy is fixed but is spread out over a bigger area as the altitude goes up, so there is smaller amount of energy per square foot. Essentially, you can increase the number of systems exposed by increasing the altitude, but percentage of systems damaged will go down. Unfortunately, while the line of site illustration is fairly common, no one really seems to have done any unclassified studies as to how damaging the 300 mile burst will be versus those at 120 or 30 miles.

  11. I personally dont think an EMP would be so terrible . In the long run for our society , it would be a blessing , electronics are part of what is dumbing out America , and making us socially retarded . I remember the days when there were no lap tops , no cell phones , and TV was black and white , with only 4 channels . You want to know what we did without all that crap ? ………….We did just fine !!!!!!!! , people were actually happier , less stressed , more social , more ethical and moral . So I say , BRING IT ON !!!!!!!!!!!!!!!!!!!!!!

    • Tolik,
      Even in what you perceive as those idyllic days, we had electric for lighting, tools, telephones, and refrigeration. Technology is only a tool and it has brought us medical equipment from pacemakers to MRI and CAT scanners. Although you may protect some personal equipment, a systemic failure of the power grid for any length of time would kill off millions of unprepared people, and allow each of us to find out how prepared we really are. I for one think that it would be more terrible than you can imagine.
      Electronics is merely a tool and the dumbing down of society is due to a change in morals and ethics, and what we will accept from each other. Although the tool may contribute, it is not the problem.

      • Rider of Rohan says:

        OP, great comment. One set of my grandparents didn’t get electricity until 1963, and I well remember as a 10-yr. old kid having to use their outhouse and them having coal-oil lanterns for light. It was fun for a couple of days, but got old quick.

      • mom of three says:

        I think you are 100 percent in your thinking. With so many unprepared it will be worse then our own imagination can come up with. With each generation, things are different case point my daughter, was born in tbe year 2000 , her and her brothet 2004 that is all they known a life with all of the computers, phones, ect. Our grandparents, were still using outhouses, and oil lamps, but even they had to march and get with the times.
        My parent’s are 74 and 76, finally got a cell phone, same principles
        you can choose what to have electronic wise and how to proceed
        with them. None of us will 100 percent escape the modern world
        we need to choose wisely.

    • rjarena says:

      I think you have forgotten that tech is what keeps things safe, i.e. controls hazardous waste, keeps chemical plants and factories from blowing up, contains nuclear reactors, etc. When these safeties are disabled, a lot of terrible poisons will be emitted and dumped into our ecosystem. I am not looking forward to that!

      • mom of three says:

        We can learn to live with less electronics, but that is a personal choice. At our family cabin, we did live like the pioneers, a wood cooking stove from the late 1800′s, a wood fireplace, we brought water up from the river to be boiled in very old teapots, we washed our hair at the river, brushed our teeth, and had the out house. The cabin, was built in 1936, and it was sold as is with what the people left in it in 1962 to my father’s family. I enjoyed that time but to live like that again for who knows how long, I would not wish an EMP on anyone. It’s been in the last 10 years, the family up dated the cabin, to have propane stove, and took the fire place out. The snow was so deep and pushed the roof in on its self , that it damaged the cabin beyond repair they started over with one wall
        in place.

  12. Brian_427 says:

    I would imagine we could also face a terrorist threat from small “suitcase” nuclear device. The Soviet version was more like the size of 2 foot lockers.I understand the yield on one of those is about 10-20 kilotons.
    Any idea what kind of EMP range that might have if detonated at 30-35 thosand feet?

  13. F. Ben Ross says:

    I have a 1970 jeep type vehicle with no modern electronics. I’m wondering how well the alternator, voltage regulator and starter would stand an EMP event.

    • While widely criticized as flawed, testing by the EMP Commission showed that only about 3-5% of cars in operation would be permanently damaged by an EMP. Cars that were shut off were not shown to be damaged. That percentage might not sound like much but imagine if 6 million cars suddenly stopped working all across the US. Up to 10-15% would suddenly stall, causing huge numbers of traffic jams, injuries, and delays. Many believe (me included) that older vehicles with less microelectronics would be less susceptible, but that hasn’t actually been proven by testing.

  14. Worrisome says:

    Simple question. If a car is not on, if common household electronics are not plugged in, are they affected by an emp?

    • Simple answer… probably no on the car (see my answer above regarding the EMP Commission testing), and yes on the electronics. An EMP has two mechanisms to cause damage, conducted and radiated. The pulse can introduce very high currents on power lines which in turn will likely damage most anything plugged in. However, the pulse can also transmit radiated energy, causing damage to electronics, even if those items were not plugged in.

  15. riverrider says:

    i’m having trouble understanding how cars are not damaged but all the other dire consequences are predicted. i understand how the grid gathers the pulse and conducts it, but if radiated energy doesn’t stop cars(consistent with research i took part in during army service, along with planes and radios) how will it damage others so badly? not disputing you, just trying to wrap my head around it. obviously i’m no rocket scientist :)

    • The question of damage to cars is a very good one. As I posted above, the best guess, and that’s all it is, is there might be 3-5% permanently damaged. That corresponds to roughly 6 million cars and trucks. Of course, other vessels, such as boats, airplanes, and trains could also experience some damage (but it’s not expected to be catastrophic). Communication systems are more likely going to be the biggest immediate impact when it comes transportation– think about planes trying to land without aid, ships trying to dock, etc. But as you pointed out the largest problem is more of a domino effect stemming from the loss of power. Electrical power is the lifeblood of every major infrastructure (e.g., banking, communications, medical care, water distribution, petroleum processing and distribution, food harvesting, etc.), so when it goes and backup systems exhaust their supplies, the world could all but shut down. Yes, many cars might still run, but without electricity there would be no gas available to fuel them. Once transportation goes, other dominos start to fall. You get the idea… everything is connected in one way or another.

  16. Believe it or not, most power companies would love to harden the grid. But to do so they’d have to raise the cost of the service provided, and the utility commisions that exist in most states won’t let them raise prices to cover beefed up infrastructure.

  17. Rider of Rohan says:

    Great article. Thank you, Dr. Bradley, for your willingness to lend your expertise, and to MD for publishing this article. I can’t wait for Part 2.

  18. UrbanCityGirl says:

    I’ve read this article twice and plan to read it again. Although I’m attempting to tell myself these days that I’m preparing for a simple (jk) economic collapse, my nightmare is an attack, perhaps in the form of EMP.

    I have zero electronic knowledge so this topic is quite interesting, though difficult to absorb for me. This article is quite a good example of how the comments to an article really adds so much to the format.

    We are hoping to add a simple solar setup by the end of the summer. But in the meantime, I’ve been working on reducing our dependence on the grid (says the woman who just finished vacuuming dog hair off the sofa).

    Thank you for the info, I cannot wait to read part 2!

  19. David N says:

    Dr. Bradley,

    enjoyed your brief article and I have tried to research the EMP effects as much as possible. I even have a few “nested Faraday cages” in which I have stored several items, one I figure very valuable is the 2 way radios.
    I do have a couple short questions. I have read some of the fiction writings on EMP events.. Seems everyone has their own own version of what will not work.
    Do you think batteries and LED lights will be effected in an EMP event?

    I also know a CME of the magnitude similar to the Carrington event could cause similar problems, I just wonder if a CME would take out our autos?

    Thank you for your time and look forward to reading the rest of your articles. please don’t keep us waiting too long… I just can’t help but feel like the clock is ticking and time is running out for us.
    I pray I am wrong, but we have made so many enemies and now the US seems to have lost our backbone..

    • Hi David,

      Great questions. A nuclear-generated EMP could harm small scale electronics, including those inside cars. That would include LEDs, but not batteries. Batteries are essentially immune to the radiated fields caused by EMPs.

      As far as solar coronal mass emissions (or other solar events), they don’t pose a threat to small scale electronics unless those electronics are plugged into the electrical grid. So cars are not going to be harmed by solar events. Nor is a small handheld radio or laptop computer, as long as they are unplugged. The big threat from a solar event is taking down the power grid.

      Hope that helps.


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