Is there a strong galactic magnetic field? My main question is: Is there a strong galactic magnetic field, perhaps driven by the supermassive black hole at the center of our galaxy?  I am also wondering if this field would be strong enough to make it so that the galaxy rotates in the way it does (with the outer stars moving faster than would be expected), and if this would be an alternate explanation for dark matter.

The thing that led me to ask this question is reading about Jupiter's magnetic field interactions with the plasma emitted by IO.  Jupiter's magnetic field forces the plasma to orbit Jupiter about as fast as Jupiter spins, and I am wondering if likewise, the supermassive black hole at the center of our galaxy "herds" the rest of the galaxy in a similar manner as per the article and image below.

http://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter#Role_of_Io
No, the galactic magnetic field is very weak, about 0.1nT.
It is able to bend the trajectory of highly-energetic charged particles and also to align dust grains across the magnetic field.

However, is too weak to affect the rotation of a galaxy.

Although the origin of galactic magnetic field is not clear yet, the supermassive black holes do not significantly influence the galactic magnetic field far from them.