  Recent observations of Galactic Black Hole Candidates (BHCs) suggest that
those that are superluminal jet sources have more rapid black hole spin rates
than otherwise normal BHCs. This provides observational support for models of
relativistic jet formation that extract rotational energy of the central black
hole. To investigate this mechanism, we have developed a new general
relativistic magnetohydrodynamic code in Kerr geometry. Here we report on the
first numerical simulation of the formation of a relativistic jet in a
rapidly-rotating (a=0.95) Kerr black hole magnetosphere. We assume that the
initial velocity of the disk is zero. We find that the maximum velocity of the
jet reaches 0.93c (Lorentz factor, 2.7) and the terminal velocity of the jet is
0.85c (Lorentz factor, 1.9). On the other hand, for a non-rotating (a=0)
Schwarzschild black hole, the maximum outflow velocity is less than 0.6c for
initial magnetospheric conditions similar to to those of the Kerr black hole
case. These numerical results show the importance of the rapidly rotating black
hole for the relativistic jet formation.
