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Flares and Nukes and EMPs, Oh My!
Background
You might have heard the term “EMP”, maybe from Newt Gingrich in a debate, or maybe from a news channel. But what is it exactly?
EMP stands for “Electro-Magnetic Pulse”. EMPs can disrupt electronics - or completely fry them - which is why they are a very serious concern. They propagate at the speed of light - light itself is an electromagnetic wave, as are radio waves or the microwaves which warmed your last lunch. The waves of an EMP are, as the name implies propagated as a very large, swift pulse. While numerous things can generate a mild EMP, we will only concern ourselves here with severe EMPs. The EMPs we should be a little nervous about are those caused by “High-Altitude Nuclear Explosions” (HANEs) or “Coronal Mass Ejections” (CMEs or solar flares that make it out to earth orbit distance). Both of these events can create an EMP which is capable of effecting huge land masses. A CME can create an EMP which can effect half of the globe, and can even (like radio waves) bounce off of the atmosphere and “bend around” to the dark side of the Earth. A CME starts as a bubble of plasma (superheated magnetized gas) which can sometimes be almost as large as the sun itself. This “bubble” is magnetically shot out of the sun like a 1 million MPH bullet, and typically takes one to three days to reach earth depending on it's exact speed. Learn a bit more of the science HERE. Some people are very worried about a CME as the sun is just starting to reach the peak of it's 11 year solar cycle. Personally, I'm not that worried about CMEs. While technically it's certainly possible, it is not probable. At least, Gulf Coast hurricanes are far more probable. The sphere around the sun defined by Earth's distance is a mighty big one, and the earth itself is a tiny speck of dust on the face of that sphere. A CME will go be directed somewhere to the sphere. That said, CMEs typically fly out on the plane of the sun's rotational axis, which is the same as the orbital plane of the planets. Thus, we are looking at a plane, not a sphere, of probability. There are other threats we face which I feel are far more probable, so to focus only on CMEs as some have done is in my opinion misguided. I view a CME as a worst case scenario, and while it is not probable it is absolutely possible.
Having said that, I have an update about 1 year later. On Feb. 9, 2013, at 0730 GMT, about two days prior to my writing this update, a small CME was cannoned out of the sun at an estimated speed of 1.8 million miles per hour on a collision course with the earth. Because it was small it did very little damage to electronics, and had it's major effect on simply making the aurora more vibrant. The point here is that even though the odds are against it, CMEs DO HIT THE EARTH. It just happened, and we were very lucky it was a tiny CME, and not a large one. Source: Space.com. The last CME to hit the earth was a mild one in 2011, and caused electromagnetic disruptions in Canada - less than two years prior.
On 7/31/2013, The Drudge Report reposted an article about a near-miss Carrington-class (in English, “OMG freaking huge”) EMP that the Earth missed by 2 weeks. Basically, a humongous CME passed directly through the Earth's orbital path at a point that the Earth passed through two weeks later. The report was titled Solar Flare Narrowly Missed Earth Two Weeks Ago.... The article is definitely worth reading. Had we been hit squarely with this latest Carrington-sized CME, the EMP effect would have been global, and it would have been absolutely devastating.
Unlike a CME, a HANE is a tiny pinpoint source from a nuke which occurs very close to us, say 100 miles from the surface of the earth, which radiates out in a sphere. A HANE's EMP effect on the ground is more like a gradated bulls-eye, where the intensity (“i”) is strongest in the center underneath the explosion and lessening with distance (“d”) per the inverse square law ( i = 1/d2 ). That means at a distance of 1 units i=1/12 so the intensity would be 1, at a distance of 2 units i=1/22 so intensity would be 1/4, at a distance of 3 units i=1/32 so intensity would be 1/9. Since a HANE nuke strike would be roughly 100 miles above ground level, replace “1 unit” with “100 miles”, “2 units” with “200 miles”, etc. Don't worry, there's no test at the end of the page, but this gives you an idea of the gradation of an EMP effect away from a HANE ground zero. (Technical note - the inverse square law does not apply perfectly due to numerous other intervening factors such as spread and magnification in the ionisphere). There are actually 3 electromagnetic effects or components to the HANE EMP which you can study further, but they hit back to back in such rapid succession they are not important for purposes of this discussion. It bears mentioning that a CME only has the 3rd EMP component. In comparing a HANE to a CME, other than the area of effect and state of war dictated by a HANE, the EMP results are from a layman's perspective generally the same, but more localized. I leave it to you to decide for yourself which scenario is more probable. I advise taking the larger of the two probabilities and preparing for it according to what you perceive the probability to be.
Whether it's a CME or a HANE, let's suppose for the sake of the discussion that whichever you believe is the more probable of the two occurs. What then happens if it's a really strong EMP that hits us (say we're at “ground zero” underneath a HANE)? Well, in a nutshell, elephant feces will hit the oscillating rotors. That car in the “EMP Pt. 2” movie clip will never run again. When electronics, anything with a circuit board, is exposed to an EMP, everything electronic stops working. Permanently. All electronics are completely fried and forever after worthless. Every car on the road, every car parked in a garage or a lot, will immediately and permanently be dead short of completely replacing all the electronics. But oops, all the spare parts for electronics components sitting in warehouse shelves will also be fried. Even if they weren't, the electronics in the delivery trucks will be fried too. Including the delivery trucks which even if working would be unable to traverse the many miles of roads filled with dead cars to replace the food on the shelves of now powerless grocery stores which would otherwise not be being looted to the bare shelves due to panicked riots in every community of every town of every county of every state affected by the EMP. This is why some talk about getting antique cars with no electronics and ham radios that work off of vacuum tubes. (Actually vacuum tube electronics have some components susceptible to EMPs and can also fry - nice thought though). According to the EMP Commission Report authorized by the Department of Homeland Security, a single well-placed nuke could wipe out all electricity to 2/3 of the continental USSA for a period which could last for years (and probably would last longer). While our military force is generally prepared for an EMP, America's civilian population would instantly be thrust into a 1800s catastrophe, but we wouldn't have the benefit of productive gardens in every backyard or local farmers with horse-drawn wagons. Autos would die in their place on roads. Airplanes, even if by some miracle their engines continued working, would have no navigation or radio equipment. Those able to find runways would not be able to gauge how far their landing gear was from the runway on landing attempts. Google ”sewage treatment plant process images” and browse the images - almost everywhere you see a pipe or an arrow is an undrawn electrical pump which will stop working (you don't really think it's all gravity-fed, do you?). Gasoline pumps would not pump, no water pumps to pump well water into water towers, no lights for hospital operating rooms, the newly burned out backup generators wouldn't turn on, no credit cards or bank teller computers could even acknowledge you have a banking account much less access any electronic funds whos information used to be stored on erased hard drives and magnetic backup tapes - so you won't see those funds for a long, long time, if ever. As you can imagine, the drop in population over the first year would be devastating, and that year would see horrors like none Americans have ever seen or imagined. It would not be the end of the world, but it would definitely be “the end of the world as we know it”.
EMP stands for “Electro-Magnetic Pulse”. EMPs can disrupt electronics - or completely fry them - which is why they are a very serious concern. They propagate at the speed of light - light itself is an electromagnetic wave, as are radio waves or the microwaves which warmed your last lunch. The waves of an EMP are, as the name implies propagated as a very large, swift pulse. While numerous things can generate a mild EMP, we will only concern ourselves here with severe EMPs. The EMPs we should be a little nervous about are those caused by “High-Altitude Nuclear Explosions” (HANEs) or “Coronal Mass Ejections” (CMEs or solar flares that make it out to earth orbit distance). Both of these events can create an EMP which is capable of effecting huge land masses. A CME can create an EMP which can effect half of the globe, and can even (like radio waves) bounce off of the atmosphere and “bend around” to the dark side of the Earth. A CME starts as a bubble of plasma (superheated magnetized gas) which can sometimes be almost as large as the sun itself. This “bubble” is magnetically shot out of the sun like a 1 million MPH bullet, and typically takes one to three days to reach earth depending on it's exact speed. Learn a bit more of the science HERE. Some people are very worried about a CME as the sun is just starting to reach the peak of it's 11 year solar cycle. Personally, I'm not that worried about CMEs. While technically it's certainly possible, it is not probable. At least, Gulf Coast hurricanes are far more probable. The sphere around the sun defined by Earth's distance is a mighty big one, and the earth itself is a tiny speck of dust on the face of that sphere. A CME will go be directed somewhere to the sphere. That said, CMEs typically fly out on the plane of the sun's rotational axis, which is the same as the orbital plane of the planets. Thus, we are looking at a plane, not a sphere, of probability. There are other threats we face which I feel are far more probable, so to focus only on CMEs as some have done is in my opinion misguided. I view a CME as a worst case scenario, and while it is not probable it is absolutely possible.
Having said that, I have an update about 1 year later. On Feb. 9, 2013, at 0730 GMT, about two days prior to my writing this update, a small CME was cannoned out of the sun at an estimated speed of 1.8 million miles per hour on a collision course with the earth. Because it was small it did very little damage to electronics, and had it's major effect on simply making the aurora more vibrant. The point here is that even though the odds are against it, CMEs DO HIT THE EARTH. It just happened, and we were very lucky it was a tiny CME, and not a large one. Source: Space.com. The last CME to hit the earth was a mild one in 2011, and caused electromagnetic disruptions in Canada - less than two years prior.
On 7/31/2013, The Drudge Report reposted an article about a near-miss Carrington-class (in English, “OMG freaking huge”) EMP that the Earth missed by 2 weeks. Basically, a humongous CME passed directly through the Earth's orbital path at a point that the Earth passed through two weeks later. The report was titled Solar Flare Narrowly Missed Earth Two Weeks Ago.... The article is definitely worth reading. Had we been hit squarely with this latest Carrington-sized CME, the EMP effect would have been global, and it would have been absolutely devastating.
Unlike a CME, a HANE is a tiny pinpoint source from a nuke which occurs very close to us, say 100 miles from the surface of the earth, which radiates out in a sphere. A HANE's EMP effect on the ground is more like a gradated bulls-eye, where the intensity (“i”) is strongest in the center underneath the explosion and lessening with distance (“d”) per the inverse square law ( i = 1/d2 ). That means at a distance of 1 units i=1/12 so the intensity would be 1, at a distance of 2 units i=1/22 so intensity would be 1/4, at a distance of 3 units i=1/32 so intensity would be 1/9. Since a HANE nuke strike would be roughly 100 miles above ground level, replace “1 unit” with “100 miles”, “2 units” with “200 miles”, etc. Don't worry, there's no test at the end of the page, but this gives you an idea of the gradation of an EMP effect away from a HANE ground zero. (Technical note - the inverse square law does not apply perfectly due to numerous other intervening factors such as spread and magnification in the ionisphere). There are actually 3 electromagnetic effects or components to the HANE EMP which you can study further, but they hit back to back in such rapid succession they are not important for purposes of this discussion. It bears mentioning that a CME only has the 3rd EMP component. In comparing a HANE to a CME, other than the area of effect and state of war dictated by a HANE, the EMP results are from a layman's perspective generally the same, but more localized. I leave it to you to decide for yourself which scenario is more probable. I advise taking the larger of the two probabilities and preparing for it according to what you perceive the probability to be.
Whether it's a CME or a HANE, let's suppose for the sake of the discussion that whichever you believe is the more probable of the two occurs. What then happens if it's a really strong EMP that hits us (say we're at “ground zero” underneath a HANE)? Well, in a nutshell, elephant feces will hit the oscillating rotors. That car in the “EMP Pt. 2” movie clip will never run again. When electronics, anything with a circuit board, is exposed to an EMP, everything electronic stops working. Permanently. All electronics are completely fried and forever after worthless. Every car on the road, every car parked in a garage or a lot, will immediately and permanently be dead short of completely replacing all the electronics. But oops, all the spare parts for electronics components sitting in warehouse shelves will also be fried. Even if they weren't, the electronics in the delivery trucks will be fried too. Including the delivery trucks which even if working would be unable to traverse the many miles of roads filled with dead cars to replace the food on the shelves of now powerless grocery stores which would otherwise not be being looted to the bare shelves due to panicked riots in every community of every town of every county of every state affected by the EMP. This is why some talk about getting antique cars with no electronics and ham radios that work off of vacuum tubes. (Actually vacuum tube electronics have some components susceptible to EMPs and can also fry - nice thought though). According to the EMP Commission Report authorized by the Department of Homeland Security, a single well-placed nuke could wipe out all electricity to 2/3 of the continental USSA for a period which could last for years (and probably would last longer). While our military force is generally prepared for an EMP, America's civilian population would instantly be thrust into a 1800s catastrophe, but we wouldn't have the benefit of productive gardens in every backyard or local farmers with horse-drawn wagons. Autos would die in their place on roads. Airplanes, even if by some miracle their engines continued working, would have no navigation or radio equipment. Those able to find runways would not be able to gauge how far their landing gear was from the runway on landing attempts. Google ”sewage treatment plant process images” and browse the images - almost everywhere you see a pipe or an arrow is an undrawn electrical pump which will stop working (you don't really think it's all gravity-fed, do you?). Gasoline pumps would not pump, no water pumps to pump well water into water towers, no lights for hospital operating rooms, the newly burned out backup generators wouldn't turn on, no credit cards or bank teller computers could even acknowledge you have a banking account much less access any electronic funds whos information used to be stored on erased hard drives and magnetic backup tapes - so you won't see those funds for a long, long time, if ever. As you can imagine, the drop in population over the first year would be devastating, and that year would see horrors like none Americans have ever seen or imagined. It would not be the end of the world, but it would definitely be “the end of the world as we know it”.
A Realistic Threat?
Regarding coronal mass ejections (CMEs) or solar flares, please scroll down to the 4 images at the very bottom of this page, look at the photographs, and you tell me if solar flares are possible. Canada had a black-out due to a solar flare in 2011. The media referred to it as “Massive” as it was the biggest in 4 years. It was actually very tiny compared to some the earth has seen. For instance, the Carrington Event in solar cycle 10 (aka the 1859 Solar Superstorm) was so strong that it melted telegraph wires across America and Europe and caught telegraph offices on fire. Aurora were seen as far south as the Caribbean Isles.
Is this all a valid, realistic threat? Allow me to share a little research with you. The facts lead to some speculation on my part and said speculation should be considered in that light.
On Feb. 2, 2010 the BBC reported that an American test to shoot down a rocket similar to Iranian technology failed. The complexity of this level of defense has been described as “hitting a bullet with a bullet”.
More recently, at least one Iranian missile-capable destroyer has already been deployed to the US Eastern Seacoast as reported Sept. 28, 2011 by ABC news. This is a known fact, so let's set that aside - Iranian missile destroyers in international waters off the US coast. Now, On Jan. 2, 2012, MSNBC reported the following:
Earlier Western reports of Iranian missile tests were that the missiles “malfunctioned” and exploded near the apex of their flight. Note that the apex of the flight arch is exactly where one would expect a HANE to explode. Note that the US is about 3400 miles wide at it's widest point, and that current Iranian missiles have an estimated range of up to 6400 miles. Do the math, Iran can easily reach any place on the continental US from either seacoast.
Thank Allah that Iran has made a “cross our hearts” promise that the nuclear technology they are hell-bent on developing is not for weapons use, huh? It it weren't for their word on the matter, we might need to fear a future high altitude nuclear detonation from an Iranian long-range missile fired from a destroyer patrolling US shores just on the short-range other side of international waters boundaries.
Now, thankfully, the US Dept. of Homeland Security has taken time away from their busy schedule of groping US Senators, strip searching grandmothers and using cool technology funded by our tax dollars to look at children naked, and has authorized a Committee to study the effects an EMP caused by a HANE over our continent. They have found that a single detonation could cause an electromagnetic pulse which takes out 50%-70% of the nations power grid (see Dept. of Homeland Security's EMP Commission Report of April 2008) which will take 2-3 years to recover from in a best-case scenario. That assumes South Korea which builds the generators has not become a satellite state of China and will still accept credit from a bankrupted nation who's survivors have spent the last 2-3 years in a pre-industrial revolution world. Talk about SHTF!
Is this all a valid, realistic threat? Allow me to share a little research with you. The facts lead to some speculation on my part and said speculation should be considered in that light.
On Feb. 2, 2010 the BBC reported that an American test to shoot down a rocket similar to Iranian technology failed. The complexity of this level of defense has been described as “hitting a bullet with a bullet”.
More recently, at least one Iranian missile-capable destroyer has already been deployed to the US Eastern Seacoast as reported Sept. 28, 2011 by ABC news. This is a known fact, so let's set that aside - Iranian missile destroyers in international waters off the US coast. Now, On Jan. 2, 2012, MSNBC reported the following:
Published at 4 a.m. ET: Iran said Monday it had successfully test fired a long-range missile during its naval exercise in the Gulf, flexing its military muscle to show it could hit Israel and U.S. bases in the region if attacked. The announcement came amid rising tension over Iran's disputed nuclear program which Western powers believe is working on developing atomic bombs.So from this we learn that Iranian naval (not land based, but naval) exercises have led to successful test firing of long range missiles - the kind the US has not been able to shoot down. So, we now know that Iran can successfully launch the same long range missiles which we know we can't easily shoot down directly from their ships, which we know they have deployed along the US Eastern seaboard.
Earlier Western reports of Iranian missile tests were that the missiles “malfunctioned” and exploded near the apex of their flight. Note that the apex of the flight arch is exactly where one would expect a HANE to explode. Note that the US is about 3400 miles wide at it's widest point, and that current Iranian missiles have an estimated range of up to 6400 miles. Do the math, Iran can easily reach any place on the continental US from either seacoast.
Thank Allah that Iran has made a “cross our hearts” promise that the nuclear technology they are hell-bent on developing is not for weapons use, huh? It it weren't for their word on the matter, we might need to fear a future high altitude nuclear detonation from an Iranian long-range missile fired from a destroyer patrolling US shores just on the short-range other side of international waters boundaries.
Now, thankfully, the US Dept. of Homeland Security has taken time away from their busy schedule of groping US Senators, strip searching grandmothers and using cool technology funded by our tax dollars to look at children naked, and has authorized a Committee to study the effects an EMP caused by a HANE over our continent. They have found that a single detonation could cause an electromagnetic pulse which takes out 50%-70% of the nations power grid (see Dept. of Homeland Security's EMP Commission Report of April 2008) which will take 2-3 years to recover from in a best-case scenario. That assumes South Korea which builds the generators has not become a satellite state of China and will still accept credit from a bankrupted nation who's survivors have spent the last 2-3 years in a pre-industrial revolution world. Talk about SHTF!
Precautions We Can Take
Other than voting out the idiot politicians who have allowed us to be possibly caught with our pants down, there is nothing you can personally do to stop it - it's too late to redo our national electronic infrastructure. There is, however, something you can do to protect personal electronics so there is something left if we do suffer from an EMP. Store unplugged electronics in a Faraday cage and pray.
A Faraday cage is a “cage” which blocks electromagnetic waves. They have to provide 360 coverage, top to bottom, front to back, right to left. There can be no break which is larger than 1/2 the wavelength of the EM wave to be blocked. That means a Faraday cage can be made of metal screening material if the holes in the screen are small enough.
Here's a video of a professor in an ungrounded Faraday cage (you can see the glass plate the cage is sitting on). Turn down your speakers before watching - it's loud!
Interestingly, he is standing on the bare metal cage and is not fried. This is because all charges in a conductor like the metal of the Faraday cage reside on the outer surface, and always rearrange themselves to cancel out the electric field in the interior. Thus, he could touch the inside of the cage without damage, but someone touching it from the outside, well, let's not think about that. Here is a professor explaining it and demonstrating it in far better detail:
A solid sheet of metal is actually preferred if airflow is not important, as managing the screen size then becomes a moot point. Since we know that EMP frequencies are very high (thus wavelengths are very short), we don't have to worry about matching screen size to half-wavelengths. We saw how the professor's microphone transmitter still worked, as it transmits a small enough wavelength to escape the cage while the AM radio did not. Because of this, large metal trashcans with tight-fitting lids have become popular as a low cost cage which can hold a fair amount of items. The problem with that is that it is not convenient to get to anything stored there, as it tends to be stacked. There is a metaphysical law called the Heap Accessibility Inversion Law which states that whatever you need will always be at the bottom. OK, not really. Also, the cylindrical shape is less than ideal as must boxes are cubical. Note that while it's not a universal recommendation, many people recommend insulating the interior (which we have seen is unnecessary) and having an independent, dedicated earth ground (8' long metal rid driven into the ground near your home's foundation and very close to where the cage will be - minimize wire length). You should not ground your Faraday cage to a metal water pipe or current electrical system ground, as that could act as an antenna in the event of an EMP, actually drawing EM waves into the Faraday cage instead of directing them around it. Again, the Faraday cags in the experiments were ungrounded.
A great alternative to a trash can is a metal storage cabinet such as those used in office settings. These can be quite inexpensive when purchased used, often have key-lock handles for security, they offer a much larger storage cavity, and (best of all) it is easy to get items such as an electric wheat grinder out of the cabinet for use when needed, and return it to the protective cabinet when it's not needed.
My friend LDSPrepper has built just such a Faraday cage. Watch this video here, and note how a properly sealed cage will block all EM waves such as radio waves:
It might be good to have a trash can cage for storing things you know you won't use unless SHTF, such as an inverter for solar panels, and keeping things like tools and kitchen appliances in the Faraday cage for when you need them. In the unlikely event an EMP hits while you are using your electric grain mill, well, hopefully you also bought a hand crank for it because the base will be shot. However, after the EMP fries everything outside your Faraday cage, you will still be able to open your Faraday cabinet, unpack and set up your solar generator to power your electric blender to make one last batch of Frozen Margaritas before the ice in your now-fried refrigerator melts. Enjoy!
The following two documents were written by an electrical engineer named Jerry Emanuelson regarding EMPs and are well worth reading if you desire further study.
* EMP Myths
* Getting Prepared for an EMP
A Faraday cage is a “cage” which blocks electromagnetic waves. They have to provide 360 coverage, top to bottom, front to back, right to left. There can be no break which is larger than 1/2 the wavelength of the EM wave to be blocked. That means a Faraday cage can be made of metal screening material if the holes in the screen are small enough.
Here's a video of a professor in an ungrounded Faraday cage (you can see the glass plate the cage is sitting on). Turn down your speakers before watching - it's loud!
Interestingly, he is standing on the bare metal cage and is not fried. This is because all charges in a conductor like the metal of the Faraday cage reside on the outer surface, and always rearrange themselves to cancel out the electric field in the interior. Thus, he could touch the inside of the cage without damage, but someone touching it from the outside, well, let's not think about that. Here is a professor explaining it and demonstrating it in far better detail:
A solid sheet of metal is actually preferred if airflow is not important, as managing the screen size then becomes a moot point. Since we know that EMP frequencies are very high (thus wavelengths are very short), we don't have to worry about matching screen size to half-wavelengths. We saw how the professor's microphone transmitter still worked, as it transmits a small enough wavelength to escape the cage while the AM radio did not. Because of this, large metal trashcans with tight-fitting lids have become popular as a low cost cage which can hold a fair amount of items. The problem with that is that it is not convenient to get to anything stored there, as it tends to be stacked. There is a metaphysical law called the Heap Accessibility Inversion Law which states that whatever you need will always be at the bottom. OK, not really. Also, the cylindrical shape is less than ideal as must boxes are cubical. Note that while it's not a universal recommendation, many people recommend insulating the interior (which we have seen is unnecessary) and having an independent, dedicated earth ground (8' long metal rid driven into the ground near your home's foundation and very close to where the cage will be - minimize wire length). You should not ground your Faraday cage to a metal water pipe or current electrical system ground, as that could act as an antenna in the event of an EMP, actually drawing EM waves into the Faraday cage instead of directing them around it. Again, the Faraday cags in the experiments were ungrounded.
A great alternative to a trash can is a metal storage cabinet such as those used in office settings. These can be quite inexpensive when purchased used, often have key-lock handles for security, they offer a much larger storage cavity, and (best of all) it is easy to get items such as an electric wheat grinder out of the cabinet for use when needed, and return it to the protective cabinet when it's not needed.
My friend LDSPrepper has built just such a Faraday cage. Watch this video here, and note how a properly sealed cage will block all EM waves such as radio waves:
It might be good to have a trash can cage for storing things you know you won't use unless SHTF, such as an inverter for solar panels, and keeping things like tools and kitchen appliances in the Faraday cage for when you need them. In the unlikely event an EMP hits while you are using your electric grain mill, well, hopefully you also bought a hand crank for it because the base will be shot. However, after the EMP fries everything outside your Faraday cage, you will still be able to open your Faraday cabinet, unpack and set up your solar generator to power your electric blender to make one last batch of Frozen Margaritas before the ice in your now-fried refrigerator melts. Enjoy!
The following two documents were written by an electrical engineer named Jerry Emanuelson regarding EMPs and are well worth reading if you desire further study.
* EMP Myths
* Getting Prepared for an EMP
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