Three-dimensional relativistic magnetohydrodynamic simulations of magnetized spine-sheath relativistic jets

Numerical simulations of weakly and strongly magnetized relativistic jets embedded in a weakly magnetized and strongly magnetized stationary or weakly relativistic ( v = c/2) sheath have been performed. A magnetic field parallel to the flow is used in these simulations performed by the new general relativistic magnetohydrodynamic numerical code RAISHIN used in its relativistic magnetohydrodynamic ( RMHD) configuration. In the numerical simulations, the Lorentz factor gamma = 2.5 jet is precessed to break the initial equilibrium configuration. In the simulations, sound speeds are less than or similar to c/root 3 in the weakly magnetized simulations and less than or similar to 0.3c in the strongly magnetized simulations. The Alfven wave speed is less than or similar to 0.07c in the weakly magnetized simulations and less than or similar to 0.56c in the strongly magnetized simulations. The results of the numerical simulations are compared to theoretical predictions from a normal mode analysis of the linearized RMHD equations capable of describing a uniform axially magnetized cylindrical relativistic jet embedded in a uniform axially magnetized relativistically moving sheath. The theoretical dispersion relation allows investigation of effects associated with maximum possible sound speeds, Alfven wave speeds near light speed, and relativistic sheath speeds. The prediction of increased stability of the weakly magnetized system resulting from c/2 sheath speeds and the stabilization of the strongly magnetized system resulting from c/2 sheath speeds is verified by the numerical simulation results.