As we sit, possible poised on the verge of a nuclear conflict in the Northern Hemisphere, maybe it's time to look at the damaging effects of the electromagnetic pulse that follows a nuclear detonation.

Apparently, if a nuke is deployed at high altitude, the EMP produced can have some rather nasty effects on our delicate electronics below.

You can also forget about the inverse-square law to protect you because some components of the EMP are not "point source" but actually generated by the interaction of gamma radiation with the earth's magnetic field. That produces a very large area of EMP which creates high flux-levels at ground-level, even though the detonation may be tens or hundreds of Km away.

For this reason therefore, it strikes me that we should all know a little more about EMPs and ways we could hopefully mitigate the damage they cause.

Apparently there are three phases to the way a nuclear detonation produces an EMP.

However, it's kind of reassuring to know that nukes detonated at or near ground level don't produce nearly as much EMP as those detonated at 30Km or so above the planet's surface. To be truly effective, a nuke designed to disrupt or destroy infrastructure by way of EMP has to be exploded pretty damned high so direct radiation and thermal damage won't be much of a risk.

During the first phase (known as E1), the detonation creates massive levels of gamma radiation which interacts with the upper level of earth's atmosphere to strip electrons from the rarefied gasses there and subsiquently induced massive currents (known as a Compton current) that creates a magnetic pulse with an extremely fast rise-time, typically 10nS or less.

The result is a burst of EM energy that spans the spectrum from near-DC to tens of gigahertz and which induces currents in any conducting material that gets in its way. The earth's magnetic field also helps contain this burst of energy, meaning even more of it ends up directed towards the surface of the planet.

This first phase is what'll fry your computer, your phone and any other sensitive devices that are not adequately screened from the EMP energy being produced.

After the first phase begins to subside, the second phase (E2) becomes prevailent and that sees the spectral composition of the EMP change markedly. Now most of the energy exists in the Khz to low Mhz range. This is because the Compton current has now stabilised somewhat and is changing less rapidly than in phase 1.

While the E1 phase lasts just microseconds, E2 lasts anywhere from hundreds of mS to as long as several seconds. Fortunately the reduced intensity and reduced spectral range of E2 means that it's easier to protect against.

The third phase (E3) can last anywhere from several minutes to tens of minutes and has a much lower average frequency, typically no more than a few Khz.

This is the phase that is likely to cause issues with longer conductors, such as power lines, pipelines and other long runs of metal. This phase could cause damage to transformers, switching equipment and other vital pieces of energy infrastructure. It can also cause fires as a result of arcing and localised heating within conductive structures.

So that's the bad news, what can we do to mitigate all this EMP energy?

The primary tool is the Faraday cage -- or a variant thereof.

In its most effective form, this consists of placing the gear to be protected inside several layers of conductive material, each separated by an insulating layer. This works by converting the magnetic fields generated by the EMP into currents within the conductive layers and those currents automatically create a magnetic field that opposes the EMP energy which creates them. Simple eh?

There are some caveats however.

Firstly, the conductive layers must be free from gaps or holes. During E1 the frequencies are so high that even small gaps,cracks or openings could allow enough energy through that the delicate electronics inside might be fried. This is another reason to use multiple layers -- so that any access holes can be staggered layer upon layer such that there's no direct path for energy to slip through.

Secondly, the devices being protected must be totally enclosed. No power leads, antennas or other wiring must be left outside the shielding.

Thirdly, the device being protected must not be in direct contact with any of the shielding material or the currents that flow in that material could also flow through the device itself.

So what happens if you're told there's going to be a nuke going off next door and you want to protect your new Nintendo Switch2 so that during the nuclear winter that follows, you'll at least be able to play some games to while-away the time while your hair falls out?

Well wrap your Switch in plastic film or bubble wrap. Then wrap that in aluminium foil, making sure that the ends are folded over and pressed down hard to provide good inter-layer contact and so that there are no gaps. Then... more plastic, more foil, more plastic... etc... until you either get tired or run out of materials.

That's it.

Put your sunglasses on, apply some sunscreen, place your head between your knees and relax until the debris has settled.

Mario... here we come!

Also, be annoyed that thanks to ever-shrinking fab technologies and the fact that so much of our gear is now infested with microprocessors, the damaging effects of an EMP will be far more brutal than they would have been backin the 1950s or 60s.

If you've got an old Morris Minor then chances are that it'll still run just fine as the ash is falling but that new Toyota Prius... not so much.

If there's an old valve radio in the shed somewhere, it would also keep running just fine (if there was any mains power) but without the bubble-wrap and foil it's most unlikely that any of your modern solid-state electronics will be anything other than ewaste.

Happy days!

Carpe Diem folks!

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