Question about EMPs

Are EMP effects line-of-sight, or do they act like a current?

I understand very little about the physics of things like this.

If an EMP caused by a massive solar flare was aimed toward Earth, would it affect just the side of the Earth that was facing the sun, or would it arc all around the planet?

Would a deliberate man-made EMP, delivered by rocket and detonated high above the Earth be any different in the way it acts than a solar flare EMP, other than size or power?

I'm not sure I'm asking this correctly, so feel free to assume.

Sounds like a valid question and stated so that I understand it... I only wish I had the answer.

...awaiting answer too

EMP effects are pretty short range, they effect a large area onlt if they are generated high enough in the atmosphere (>few 100km) such that the particles produced can spread over a large area as they arrive at the surface.

The local range of the effects of particles arriving at the surface is similair to that of lightning. You can think of an EMP device as the equivalent of starting a large number or lightning strikes over a large area (although EMP does not cause lightning).

Solar flares do not generate EMP, they do produce an electric current in structures near the poles and do inject low energy particles into the atmosphere - again mostly near the poles.

http://eo.nso.edu/MrSunspot/answerbook/polarity.html

An EMP would be much more localized than a massive solar flare. The Carrington Event is quite a scary proposition. Basically, if it conducts a current, then it's vulnerable. On the local scale, I think the EMP would be more catastrophic, but on a larger scale, the CE would probably cause more damage as it raced through the power lines.

Okay, so they're not the same thing... always learning something new.

Looking around online, I found this article on nuclear EMPs which also talks about solar flares (http://www.futurescience.com/emp.html)...

He talks about the Starfish Prime test in 1962 in the Pacific: "The Starfish Prime test knocked out some of the electrical and electronic components in Hawaii, more than 800 miles away. The damage was very limited compared to what it would be today because the electrical and electronic components of 1962 were much more resistant to the effects of EMP than the sensitive microelectronics of today. The magnitude of the effect of an EMP attack on the United States will remain unknown until one actually happens... the magnitude of the all of the components of an EMP are roughly proportional to the strength of the earth's magnetic field. The earth's magnetic field over the center of the continental United States is about twice the strength as at the location of the Starfish Prime test."

The part on solar flares: "Solar flares can also cause current overloads on the power grid that are very similar to the slower E3 component of a nuclear electromagnetic pulse. There is good reason to believe that the past century of strong human reliance on the electrical systems has also, fortunately for us, been an unusually quiet period for solar activity. We may not always be so lucky.

[refers to the 1859 Carrington Event] "... if such a geomagnetic storm were to occur today, it would shut down the entire electrical grid of the United States. It is likely that such a geomagnetic storm would destroy most of the largest transformers in the electrical grid. Spares for these large transformers are not kept on hand, and they are no longer produced in the United States."

While the author is most interested in indicating how these to problems would affect the U.S., is he also seems to be saying that the effects would be somewhat limited, as in all of N. America, all of Europe, etc?

But then he goes on with "A solar storm of the size of the 1859 event, or even a smaller geomagnetic storm that occurred on May 14-15 in 1921, could simultaneously knock out the power grids of the United States, Canada, northern Europe and Australia, with recovery times of 4 to 10 years (since the solar storm would burn up large transformers worldwide, for which very few spares exist.) The United States has no capacity for building replacements for these large transformers."

If I am understanding all of this correctly, would he be indicating that only the half of the world facing Sol would be affected by a solar flare?

It is best to think of an Electro Magnetic Pulse as a very short burst from a very strong radio broadcast. What happens is just like the radio waves from a broadcaster causing a small electric current in your radio antenna. Your radio or TV picks up those voltages and currents from the antenna then amplifies them to make the sound you hear.
The EMP creates a very strong set of current because the EMP device is much much more powerful than a radio broadcaster's station.
The voltage and currents it makes are strong enough to fry diodes, capacitors and especially transistors. Modern electronics are all chip based. Electronic chips are super miniaturized arrangements of capacitors, diodes, and transistors with some really fine transistors in the mix. Because they are so small they are much more likely to be fried by the high voltages and current than old systems with heavier components.
(We usually do not think about the chip having the same things in it as a normal circuit but cause they are all microscopic in size and sold as an integrated circuit chip.)

The EMP is normally short wave lengths too. The chips do not need to be connected to a proper antenna to fry. Almost any wire connected to them will do, even the line printed on a circuit board can act as an antenna. That is why they recommend placing radios etc inside a metal box. The hope is for the box to act as a Faraday cage and shunt the magnetic wave around the electronics.

EMP as a weapon is one of the great untried experimental weapon systems.
If anybody has tried using one they have never published the results.
Experiments with EMP which have been published are not totally convincing about how effective it would be.

Not all chips fry, not all radio tubes are immune.

Yes, a CME could last 24-48 hours and so would give most of the Earth time to enjoy it.

I'm sceptical about the claim that all the transformers would melt, powergrids have a lot of safety systems to protect them from natural events and idiots. The huge blackouts seen in the US and Canada are precisely because of this - at the first sign of anything bad happening systems disconnect everything - leaving people without power, but preserving the infrastructure.

It takes a deliberate level of stupidity to force the system to damage itself - Enron and unregulated markets for power transfer are more effective than an EMP.

I sincerely hope you are right.

From what I've read, I suspect grid transformers to be some of the most vulnerable. They are directly connected to some of the best long-wire antennas out there (high voltage transmission lines) and with the quick rise-time of an EM Pulse, their protective circuitry won't have time to do its job. Just about anything else can be locked away in a SEA-LAND container, but the grid itself is just out there.

Susan, you may want to google "Perfect Disaster" "solar storm". Perfect Disaster is a series on the Discovery Channel. Very good layman's explanation. There is a great explanation of the burning out of transformers.

Indeed, although the article refers to a solar storm, and not an EMP event, the effects on grid transformers would be similar.

EMP is a pulse of electromagnetic energy produced by a nuclear detonation, A solar storm is a natural event, that induces undesirable currents in long conductors such as grid lines.

A solar storm would only damage transformers connected to grid lines, spares or units switched out for maintenance would be safe.
However only a very few spare large transformers exist, and they are manufactured to order.
Smaller transformers are less of a problem since utilities hold stocks of spares, and they can be manufactured readily.

The EMP event is more concentrated than a solar storm.
EMP could kill a radio or TV connected to an aerial, a solar storm would only damage equipment connected to long grid lines.

Beyond normal disaster preps (food, water, fuel, shelter, defence etc.) there is nothing that an individual can do about solar storms.
Individuals can however prepare, at least to some extent for EMP events.
Spares should be stocked of useful electronic goods such as radios, landline telephones, GPS units, solar charge controlers etc etc. These should be stored completly enclosed in metal which will at least partial protect against EMP.

Man, I just don't know where you folks are getting your information, but it is worse than useless, it is wrong, flat wrong.

It doesn't matter what the source of the emf field is. It could be lightning, it could be a solar storm, it could be an ionizing atomic discharge, it could be someone forgetting to run the switchgear improperly at the substation. If the field exceeds the dielectric limits of the insulation in a transformer or a motor or just a plain old coil, or if it exceeds the PIV of a diode junction, then that device is going to fail. Once the insulation on a coil is breached, you essentially have a short circuit condition across the windings, and the first time a constant current is applied across that coil, it is going to either blow open at the short, or fry altogether in a catastrophic failure. Once the diode junction is punched, the semiconductor becomes just another resistor and the junction will fry and blow open. As for induced current, if the emf potential is not too high but is sustained long enough that a spurious current of sufficient size hits the coil or the forward biased diode, it can cause excessive current and thereby overheat the device and also result in a failure. EMPs aren't typically long dwell time events, but by their nature they can accumulate a current in a long wire network that results in a sustained current flow condition that can be just as bad as a solar storm.

It doesn't matter if a device is in circuit or sitting on a shelf in a bin somewhere. EMP and solar storms can and will fry the compnents just as quickly on the shelf. Longwire impulse won't be a factor out of circuit, but the excessive voltage will be. Sometimes even a faraday shield/screen/cage isn't sufficient to protect the component. The surest protection for any component is to have as close to an infinite ground on all the leads as close to the component as possible. The ground will shunt the induced voltage and current. It still may not be enough, but it is your best chance at saving electronic components. That means the component has to be out of circuit. Barring that, a deep and well grounded Faraday cage is your next best chance.

benjammin: Not to be a wise guy, just asking a question.

What if less say parts for a car were bured under ground, in a water proof container. and let me also say that EMP is leat of my worry. If that happens there will be other pressing problems.

It depends on the ground potential around the container, which takes into consideration ionic mineral content, moisture, density of material, area/volume etc. In addition, the emf field strength determines the effective penetration of the field.

Bascially, it is how deep you bury it, how conductive the material is you buried it in, and how far the conductive material spreads out without encountering a less-conductive area. Also, how big the EMP is and the proximity to it. Under ideal conditions, underground burial can be highly effective at protecting electronics. However, if the equipment is still hooked up to an outside supply source that the EMP could get to, the equipment and it's components can still be compromised.

Thanks

I can not agree that a grid transformer, disconnected from the grid is vulnerable to solar storms.

The voltages induced by a solar storm, per yard, are very modest, and far below the normal operating voltage.
If however the transformer is connected to long conductors as would be the case whilst in use, then damaging voltages would be induced.

I would respectfully point out that a moderatly severe solar storm caused blackouts in Canada and the nothern parts of the USA some years ago.
Several transformers and other items connected to the grid suffered damage.
I am not aware of any electrical equipment being damaged whilst sitting on the shelf.

An EMP event produces greater electric fields, and can damage unprotected electronics, and might damage heavy electrical equipment.

Portable electronic equipment if totally enclosed in metal should survive all but the very worst EMP event.
Should certainly survive anything that the owner can survive.

Adam2,

With common solar storm activity, I would tend to agree with your conclusion. If however we are considering a large magnitude X class flare, then all bets are off on amplitude. However, such events are very rare, and have other far more immediate consequences. My point is that the sun is capable of producing solar activity sufficiently strong to match the signal amplitudes found in EMPs

It's been my experience that metal cased equipment, whether referring to the chassis alone or placing the equipment in another metal container, provides only limited protection. If the metal case is grounded, the protection is improved, and could be enough to negate lower EMP amplitudes. It is scalarly proportional, and some protection is always better than none. My contention is that by the nature of the threat, at or near the very worst EMP event is a likely outcome should the threat manifest.

Yeah, the green boys have all the best toys...

Okay, off on a tangent...

Does anyone remember who said about space aliens something like "We always assume that they're smarter than we are, but not as good-looking"?

Here's an interesting article for you.

http://www.scientificamerican.com/article.cfm?id=bracing-for-a-solar-superstorm

That is a very good article. I accidentally threw away that issue and ordered it again to have it.

For the solar storm issue, I do remember that the polarity (which is unknown until it hits) plays a major role. If I remember correctly, it was a negative polarity which can be devastating.