From your link:


An electrical tether uses the same principles as electric motors and generators. Move a wire through a magnetic field and you get an electrical current for power.


That's Faraday's Law of Induction - to which I explicitly referred in my last post. It's about the relative motion between a conductor and an external magnetic field.


An electrical tether will work only where nature provides both a magnetic field and a plasma (electrified gas). The motion of the wire through the magnetic field provides the energy, and the electrons in the plasma provide the return path that completes the electrical circuit.


Again, as mentioned in my last post - you need a plasma to complete the circuit, for current to flow.

Still, the link did provide a clue to the specific question I've been asking all along:

Send electricity through a wire and you get a magnetic field that drags or pushes on any outside magnetic field.


Yes, the electric current induced in the conductor sets up its own magnetic field. That reminder was enough to jig my memory of basic EM physics - it's all about Lenz's Law: "For a current induced in a conductor, the current flows in such a direction that its own magnetic field opposes the change that produced it."

That's what I was looking for, but I ended up having to find it myself. Anyway "my bad" for forgetting Lenz's Law in the first place. Can't blame anyone else here for not knowing - at least those without formal physics education.