mollwollfumble said:
In case you’ve wondered how a black hole can have a magnetic field at all …
Think about it, information about magnetism propagates at the speed of light by electromagnetic waves, and no electromagnetic wave can escape from inside the event horizon of a black hole. So it would seen that no black hole can have a magnetic field.
Hee hee hee. I’m winding you up …
A black hole can have not just one magnetic field but two. Two dipole fields that are not necessarily aligned with each other.
Can you see how? …
OK, enough of the mystery.
When a black hole is both rotating (common) and charged (rare) then it has a dipole magnetic field because it has the charge in orbit within it undergoing a fearsome acceleration as travels around in its orbit. The fact that the magnetic field can’t be “radiated” because electromagnetic waves can’t escape is beside the point, because the magnetic field is, like the gravity, frozen onto the event horizon as viewed from a distant observer.
The second dipole magnetic field can come from ionised material orbiting the black hole outside the event horizon, the ionisation is because electrons are lighter in weight than protons so are shed like in a cathode ray tube when the orbiting material is heated.
The two magnetic fields are not necessarily aligned.