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Magnetically driven superluminal motion from rotating black holes

We have investigated magnetically driven superluminal jets originating from rotating black holes. The stationary, general relativistic, magnetohydrodynamic wind equation along collimating magnetic flux surfaces has been solved numerically. In particular, we apply our results to the Galactic superluminal sources GRS 1915+105 and GRO 1655-40. Our results show that the observed speed of more than 0.9 c can be achieved in general by magnetohydrodynamic acceleration. The velocity distribution along the magnetic field has a saturating profile. Further, we find that highly relativistic speeds can be reached also for jets not emerging from a region close to the black hole, if the flow magnetization is sufficiently large. The plasma temperature rapidly decreases from about 10**10 K at the foot point of the jet to about 10**6 K at a distance of 5000 gravitational radii from the source. Temperature and the mass density follow a power law distribution with the radius.