There are a couple of things going on in this thread. One is EMP, the flash of electromagnetic radiation that comes from a nuclear weapon being detonated. Those will flash fry your chips and circuits (not to mention you) and render all these things useless. The EMP will travel hundreds of miles beyond the actual blast radius of a nuke, although like anything else it dissipates with distance.
This is similar, but unlike a solar coronal ejection; same principle but dispersed over a much wider area, for much longer time, but at a much lower intensity. An SCE will not fry most (*) electronics, but can induce power into any long metallic artifices, including telephone lines, cable, electric power lines, even pipelines. That is where the danger lies, because that induced power will go somewhere and as luck would have it probably right into the back of your TV. A cell phone, sitting in your back pocket, has little to fear from an SCE, although the towers and longlines back to the CO certainly do- so the whole system might stop working even if your phone is fine.
If you hear of it coming, unplug. There’s very little else you can do, unless you live next to a junkyard and have enough time to build metal shielding around everything.
Question: In case of a warning of an SCE, would it be enough to flip the main house breaker? Or does each piece of equipment (TV, computer, etc.) need to be shut off since the long wires would act as antennae?
No, that probably would not be sufficient, depending on the strength of the plasma cloud.
As I understand it, any wire could be subject to an induced current, however it’s “the longer the wire the more current can be induced.” Therefore the 6 foot plug on your computer probably is irrelevant The 100 foot wire from your panel to the outlet might be. The 400 yard run from the transformer to your house surely would be.
As in so many things, “size matters.”
This is really an elementary concept: run a magnet near a wire, you induce an electrical current; It’s the basis of every generator ever. The Coronal Mass Ejection is really just electric/magnetic particles flowing past wires (or other long metallic structures), and inducing an (unwanted) current into them, over and above what the wire is expecting to hold.
Unplug everything you can. I will try not to get into the physics weeds. EMP stands for “electro-magnetic pulse”. Lightning can generate them, and nuclear detonations absolutely generate them. A SCE is basically a plasma which sends a surge of ionized (charged) particles outward. A moving charged particle generates an EM field.
Whenever an EM field crosses a conductor, it generates current. If the conductor is big enough (like power lines, or even the wiring in your home), and the EM field large enough, the current will blow out items connected to that conductor (e.g. your TV, your refrigerator compressor, computer equipment, etc).
So, flipping the breakers in your panel won’t do a lot. It won’t address the in-home wiring at all, and a large surge from the power lines might actually jump the breakers. If you unplug your stuff, then the only currents you have to worry about would be induced within the device itself (e.g. your PC).
An SCE would have to be extraordinarily large to affect Earth-bound equipment due to our atmosphere, and our magnetic field. I think the last one occurred over 100 years ago, and we weren’t reliant on electrical devices like we are now. Satellites are another matter, as well as the ISS. They could get fried.