Three‐dimensional Magnetohydrodynamic Simulations of Relativistic Jets Injected into an Oblique Magnetic Field
We discuss the structure and relativistic kinematics that develop in three spatial dimensions when a moderately hot, supersonic jet propagates into a denser background medium and encounters resistance from an oblique magnetic Ðeld. Our simulations incorporate relativistic MHD in a four-dimensional spacetime and clearly show that (1) relatively weak, oblique Ðelds (at 1/16 of the equipartition value) have only a negligible inÑuence on the propagating jet and they are passively pushed away by the
... relativistically moving head ; (2) oblique Ðelds in equipartition with the ambient plasma provide more resistance and cause bending at the jet head but the magnitude of this deÑection and the associated backÑow are small compared to those identiÐed by previous studies. The new results are understood as follows : Relativistic simulations have consistently shown that these jets are e †ectively heavy, and so they do not su †er substantial momentum losses and are not decelerated as efficiently as their nonrelativistic counterparts. In addition, the ambient magnetic Ðeld, however strong, can be pushed aside with relative ease by the beam, provided that the degrees of freedom associated with all three spatial dimensions are followed self-consistently during the simulations. The e †ect is analogous to pushing Japanese "" noren ÏÏ or vertical venetian blinds out of the way while the slats are allowed to bend in three-dimensional space rather than as a two-dimensional slab structure. Applied to relativistic extragalactic jets from blazars, the new results are encouraging, since superluminal outÑows exhibit bending near their sources and their environments are profoundly magnetizedÈbut observations do not provide support for irregular kinematics such as large-scale vortical motions and pronounced reverse Ñows near the points of origin.