We know about the theory that the world’s magnetic field is from a molten iron core that flows and produces a dynamo type effect which results in earth protective magnetic field, but is it possible to use very large induction coils to harness that field?
To be effective in other areas it would need to be a reasonable height above the ground, and preferably in an area of magnetic instability that has its own local field. Using the normal earth’s field would be particular to positioning. Since it is a magnetic field then it would be quite possible to use it in the opposite way, and using a carrier field you could even use it for worldwide communication without all this silly satellite business and line of sight.
There used to be a system used in metal detectors called ground effect balance that tried to counter the changing fields as people searched for metal objects, discriminating for the correct frequencies, but this GEB has a potential to be used, especially if signals could be captured and retransmitted by the earths metallic core.
How About a Giant Induction Coil at the poles or an Area of Magnetic Flux
I have never been sure that the earth’s magnetic poles have not changed quite recently in its history. Most theories about this are based on paleomagnetism, but if the changes we such that they moved back and forth within the time for a rock to become stable and solidify in very large flows, we would not be aware of it. The key is how small must a formation be so that it will align and how long does it take to give magnetic coherence? Such events may only be possible over very long periods. How long would say a limestone deposition take to form a depth that is significant and can’t easily be altered from its original orientation? 100 years, 10,000 years. So there is a possibility that in the past this has happened many times and frequently, only permanent and long term events showing up. The earth’s surface moves around all the time in different directions, not necessarily consistently, and possibly changing direction within even 100 years as plates move and faults give way.
Has and embedded coil already been done, maybe damaged or destroyed by plate and fault movement, but inactive? Or if as it looks like major magnetic events seem to be happening we might rediscover past systems that suddenly become active again.