Numerical Simulations of Relativistic Jet Formation in Kerr Black Hole Magnetosphere

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Relativistic jets from several kinds of objects in the universe have been found. It is believed that they are all formed by violent phenomena near the black holes. Among the proposed mechanisms, the magnetic mechanism of the jet formation is becaming most promising because it may explain not only the acceleration but also the collimation of the jets. However, the distinct mechanism has not yet been shown. To investigate the magnetic mechanism, we have developed the general relativistic magnetchydrodynamic (GRMHD) simulation code.First year of this research project, we have performed the GRMHD simulation of the rather simple system consisting of the Kerr black hole, rare uniform plasma, and the strong uniform magnetic field. The result dearly showed the strong power radiation from the black hole through the magnetic field. It also interestingly showed the magnetic mechanism of the energy extraction of the black hole. However, most of the plasma falls into the black hole and no jet is formed. Then, next we performed the GRMHD simulation of the cases with the radial magnetic field and the magnetic field induced by the electric current loop near the black hole. With these calculations, we have succeeded to show the relativistic outflow, whose velocity is larger than 90% of light speed. Especially, in the current loop magnetic field case, the magnetic flux tubes bridging the region between the ergosphere and the accretion disk around the black hole are twisted by the frame-dragging rapidly. The increase in the magnetic pressure in the magnetic tubes (magnetic bridge) causes the explosive expansion of the magnetic bridges. The numerical results show that the expansion produces the relativistic outflow. In conclusion, the magnetic bridge between the ergosphere and the accretion disk around the Kerr black hole never be steady-state and should be connected to the relativistic jets directly.