Blandford-Znajek mechanism

A theoretical mechanism proposed by Blandford and Znajek to explain the radio jets associated with the active nuclei of galaxies and in particular the prodigious energy radiated by quasars. An accretion disk coupled with a rotating black hole causes electric currents and magnetic fields to appear, caused by the friction of the gases pouring into the central rotating black hole, called a Kerr black hole. By a process similar to a dynamo, the rotational energy of the black hole can thus be extracted.

http://www.spacetelescope.org/videos/html/mov/320px/heic0409a.html