The following is to correct what I wrote in the past, and to explain
where the assumptions that I was making were wrong, and to summarize
my current understanding.
John wrote:
> Unless someone has figured out how to violate the laws of
> thermodynamics and conservation of energy, the effective strength
> of an emp attack must vary invesely with the square of the
> distance as well. The only way that this could be violated is if
> the emp attack is targeted -- that is, if the attack is a vector
> targeting a single city. But if the emp attack is supposed to
> attack the entire country from California to Washington to Maine
> to Florida, then all of the energy from the emt explosion would
> have to be spread over the entire 3.5 million square miles. So if
> the strength of the emp explosion is X, then the strength of the
> attack per square mile is X/3.5 million.
OK, so the incorrect assumption that I was making when I
wrote the above was that the electronic devices would be fried
by some sort of energy from the emp explosion. I didn't see how
it was possible for a single emp explosion to produce enough
energy to fry electronic devices all over the company.
John wrote:
> OK, so I guess that explains it. An emp blast over North Dakota
> would result in the E1 electrons being sprayed over the entire
> country, from California to Maine, and fry all the
> electronics.
Higgenbotham wrote:
> Electrons generated close to the earth's surface and hitting
> nearly all at once at nearly the speed of light is about as bad as
> it gets, as far as a mechanism goes for frying electronics. Beyond
> that, that mechanism is way too complicated for somebody like me
> to have a clue as to how to quantify it in order to know whether
> thresholds would likely be exceeded.
It takes energy to fry an electronic circuit, and I assumed that the
energy would have to come from the emp blast. But the energy required
to fry the electronics would not come from the explosion at all. It
would come the electric power being used by the electronic devices
themselves, when they are running. This also explains why electronic
devices that are turned off would not be affected.
Commission to assess threat to US from EMP attack wrote:
> Automobiles were subjected to EMP environments under both engine
> turned off and engine turned on conditions. No effects were
> subsequently observed in those automobiles that were not turned on
> during EMP exposure. The most serious effect observed on running
> automobiles was that the motors in three cars stopped at field
> strengths of approximately 30 kV/m or above. In an actual EMP
> exposure, these vehicles would glide to a stop and require the
> driver to restart them. Electronics in the dashboard of one
> automobile were damaged and required repair. Other effects were
> relatively minor. Twenty-five automobiles exhibited malfunctions
> that could be considered only a nuisance (e.g., blinking dashboard
> lights) and did not require driver intervention to correct. Eight
> of the 37 cars tested did not exhibit any anomalous response.
>
http://www.empcommission.org/docs/A2473 ... on-7MB.pdf
This would seem to imply that an emp attack could harm or
inconvenience a lot of people on an individual basis, but would not
harm the country as a whole.
I was about to say that China today might launch a more powerful emp
explosion, or multiple emp explosions. But wait a minute. The size
of the emp explosion is irrelevant, since the damage is done by
free-falling electrons. Furthermore, if there are multiple attacks,
would the electrons from multiple attacks do more damage than the
electrons from one attack? It would seem by the Law of Diminishing
Returns that subsequent attacks would be far less marginally effective
than the first one.