3-DIMENSIONAL MAGNETOHYDRODYNAMIC SIMULATIONS OF RELATIVISTIC JETS INJECTED INTO AN OBLIQUE MAGNETIC-FIELD

We discuss the structure and relativistic kinematics that develop in t hree spatial dimensions when a moderately hot, supersonic jet propagat es into a denser background medium and encounters resistance from an o blique magnetic field. Our simulations incorporate relativistic MHD in a four-dimensional spacetime and clearly show that (1) relatively wea k, oblique fields (at 1/16 of the equipartition value) have only a neg ligible influence on the propagating jet and they are passively pushed away by the relativistically moving head; (2) oblique fields in equip artition with the ambient plasma provide more resistance and cause ben ding at the jet head but the magnitude of this deflection and the asso ciated backflow are small compared to those identified by previous stu dies. The new results are understood as follows: Relativistic simulati ons have consistently shown that these jets are effectively heavy, and so they do not suffer substantial momentum losses and are not deceler ated as efficiently as their nonrelativistic counterparts. In addition , the ambient magnetic field, however strong, can be pushed aside with relative ease by the beam, provided that the degrees of freedom assoc iated with all three spatial dimensions are followed self-consistently during the simulations. The effect is analogous to pushing Japanese ' 'noren'' or vertical venetian blinds out of the way while the slats ar e allowed to bend in three-dimensional space rather than as a two-dime nsional slab structure. Applied to relativistic extragalactic jets fro m blazars, the new results are encouraging, since superluminal outflow s exhibit bending near their sources and their environments are profou ndly magnetized-but observations do not provide support for irregular kinematics such as large-scale vortical motions and pronounced reverse flows near the points of origin.