[T-A]

No. Optimal altitude for an EMP attack is actually a few hundred kilometers up. The "base case" usually considered in these scenarios is a nuke going off about 400 km over Omaha. At that altitude, the ionosphere helps you create a "slow" E3 pulse which induces a field in the tens of volts per kilometer at ground level; and since you can see most of the continental US, you have plenty of kilometers to work with.

[tgsovlerkhgsel]

https://commons.wikimedia.org/wiki/File:EMP_mechanism.png shows a field strength of 25 kV/m for most of the US.

My understanding could be wrong, but wouldn't this mean exposing a 1 cm wide component (and/or components that have one cm long traces attached) to at least 250 V?

Wouldn't this be expected to destroy not every single component, but enough components to make enough hardware inoperable to collapse all industrial and power generation capabilities? (If you destroy 10% of ICs on only 10% of control boards in a power plant or factory, I'd assume that plant goes down hard and isn't coming up any time soon.)

[T-A]

> 25 kV/m for most of the US

That's the first (E1) pulse. And yes, the general idea is that it fries your electronics. Then the E3 pulse arrives and wrecks the electric network.

[ideals]

400km is LEO territory for satellites. Does this mean anything not in eclipse at that time is fried or blown up?

Also wouldn't that start/accelerate the Kessler Syndrome

[ben_w]

From what I’ve read about Project Orion, the physical damage from nukes is mostly in the shockwave. The material shockwave doesn’t propagate very far in space, so satellites won’t be blown up by a space nuke.

The EMP is, if I understand right, created by a shockwave in the extremely diffuse plasma of the ionosphere, affecting electrons and ions differently, creating a massive charge separation, and the collapse of that charge separation is what produces the actual EMP. That said, this article is the first I heard of the E1/E3 distinction, so I don’t know enough to be sure of what an EMP would do to satellite electronics.

[baybal2]

That long wave EMP was only a threat to early unprotected powerlines, not electronics.

What is a threat to electronics are VHF pulses from initial xray burst from the bomb.

[tgsovlerkhgsel]

What's the range of that pulse, and how does it relate to the field strength map seen on Wikipedia (https://commons.wikimedia.org/wiki/File:EMP_mechanism.png)?

Naively, this map makes me think that a single such EMP means enough electronics break that every major power plant or industrial plant is down and not recoverable for weeks.

[T-A]

The protection is provided by Digital Protection Relays (DPRs) which can be fried by the E1 pulse; then the E3 pulse arrives.