[MikeS (OP)]

If a rotating black hole had charge then presumably it would have a magnetic field. 

Could this magnetic field be felt outside the event horizon?

[CliffordK]

I believe the magnetic field is non-particle related, thus a gravity well should not prevent it from being expressed.

However, that might bring up the question what a black hole is.  Is it a gravity well so great that photons are too massive to escape.  Or is it a point where space is expanding/contracting at a speed faster than the speed of light, in which case, if a magnetic field propagates at the speed of light, it could not escape.

[yor_on]

A very interesting question.

Take a look at. at this even though it's a paysite and here for a description of 'magnetic field lines in a Black Hole Plasma Disc.'

[MikeS (OP)]

I believe the magnetic field is non-particle related, thus a gravity well should not prevent it from being expressed.

However, that might bring up the question what a black hole is.  Is it a gravity well so great that photons are too massive to escape.  Or is it a point where space is expanding/contracting at a speed faster than the speed of light, in which case, if a magnetic field propagates at the speed of light, it could not escape.

I don't see why. Anything close enough to the event horizon gets sucked in, it does not have to have mass..

As I see it, if space time is so highly warped (curved) that not even light can escape then no field (other than gravitational) can propagate through it and that includes magnetic and charge.

I see no reason why a black hole should not have a magnetosphere but only if it originates outside the event horizon.