EMP/CME

What is an EMP?

An EMP is an abbreviation of ElectroMagnetic Pulse. This phenomenon occurs naturally (such as a lightning strike) but in the context of emergency preparedness and concerns, it is usually referring to a byproduct of a nuclear explosion.

This is known as an H-EMP, as is written about in the fictional novel, One Second After. Now disbanded, the EMP Commission was formed within the government during 2001 and tasked with exploring this potential disaster further. The report, in short, stated that the majority of the population would be dead within a year due to cascading effects of infrastructure failure. It is worth noting this same result can be achieved without using nuclear methods in the form of a successful cyber attack, which, in my opinion, is infinitely more likely.

In short, detonating a nuclear device in the atmosphere would cause an incredible surge of energy that would damage or destroy most electronic items connected to the grid, or otherwise unshielded.

An EMP fits into what is called a low-likelihood, high-causality event, such as a large earthquake, for this reason. Extreme low likelihood of occurring, but if it does, the results are catastrophic.

Now on to more about an EMP. Due to how the radiation generated from the device interacts and propagates within the atmosphere (it's called the Compton Effect) a successful HEMP would essentially fry sensitive electronics within its range in the area beneath the detonation (hundreds of miles/kilometers depending on altitude.) For a HEMP, it is irrelevant if the device is plugged in. If the device contains microprocessors, it is at risk, turned off or not. Computers, cell phones, GPS, etc.

Who would an EMP/CME affect?

Since an H-EMP is a localized phenomenon, the effects would be limited to line of sight. That may be a small area, or potentially a continent-sized zone. A Coronal Mass Ejection would be a worldwide phenomenon.

How to Prepare for an EMP?

The primary (reasonable) way to protect against this is a Faraday cage. (Such as a metal trash can with a tightly-sealing lid, or multiple layers of tin foil that aren't contacting the device being protected) This provides a barrier that outright blocks the frequencies from interacting with the devices placed inside (as long as they're not touching the walls of the cage.) It is disputed if grounding a Faraday cage is necessary, and there are vehement arguments on both sides. Creating a 'nested' Faraday cage is also possible- a Faraday cage within a Faraday cage (tin foil-wrapped boxes within a metal trash can, for example)

A microwave is not an effective, wide-spectrum Faraday cage. In practice, it is a specific-frequency Faraday cage (hence how it heats the food and not the face of someone watching it,) but it would not protect against the wide spectrum of waves generated by an EMP. A good test for a Faraday cage is to get a good radio, tune it to the lowest AM station available, and place it inside the cage. If you don't hear anything, then it is blocking the frequencies. Repeat this test for low FM, and then high AM/FM stations.

A common question is regarding cars during an EMP. The EMP Commission did studies on this, and it is extremely likely a car would be rendered useless. The below links explain why the cars in the report started back up. Simply put, the Commission couldn't afford to destroy them, and therefore limited the tests. Their personal accounts indicate cars could, and would be absolutely destroyed.

From a now-offline interview, Dr. Peter Vincent Pry (head of the EMP Commission) stated that the cars utilized in the tests were borrowed and could NOT be fully tested. As soon as something was starting to fail (at low levels), they stopped. They couldn't afford to buy 25 cars/trucks to see them tested to the full EMP levels.

A summed up quote is -

That is from the EMP Commission, and I am inclined to take their word over claims that cars 'might' be grounded, etc. Cars nowadays have much more integrated electronics than 10+ years ago. Vehicles that are pre-electronic fuel injection (1980's), are less likely to be affected by an EMP, and should be considered if that is a concern.

Dr. Pry was gracious enough to answer a follow-up question concerning cars. He confirmed that the cars would likely be damaged/destroyed, but pointed out that it's somewhat moot. A successful EMP would render roads utterly impassable due to accidents and traffic due to the EMP.

What is a CME?

A CME is a burst of radiation from the sun, simply put. In this case, it would largely affect only devices plugged into the electronic grid. That, or which contain a long antenna. No Faraday cage is necessary in this case and will largely affect power stations, transformers, etc. There will likely be a warning prior, as such energy takes time to reach Earth (hours.)

In either case, if large transformers are destroyed the power infrastructure of the U.S is likely to be down for months if not over a year. This is due to large transformers not being stored in backup locations (due to cost, size, and specific design,) as well as the original ways that the devices were transported no longer exist in some cases (rail lines.) This is elaborated in Ted Koppel's book, Lights Out, which delves into the preparation against a Cyber-attack, something that would achieve a similar, long-term result as an EMP without the nuclear device. That is not the focus of this page however.

How to build a cheap but decently effective Faraday cage?

Metal trash can with a tight lid + sealing the seams with metallic tape/solder is what I have. Total cost. like 30ish bucks. Insulate items inside wrapped in foil to created a 'nested' Faraday cage (Faraday cage inside a Faraday cage.)

I saw a comment on the link below that someone bought a 30 gallon can, sprayed foam inside it, then put a 20 gallon inside and sealed both lids. I will personally upgrade to that since it's such a good idea.

Grounding isn't necessary and may conduct the waves into the cage, from what I understand. Cheap, easy, and low stress. An EMP is an extremely low-likelihood, but high impact event. While not worth discounting, it's not worth breaking the bank over preparing for. (Versus more common, likely disasters such as job loss, civil unrest, etc.)

Video of a rough test

Sources:
EMP Commission official reports

Additional resources:
What is an EMP
EMP vs CME