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P. A. Hughes (U. Michigan), M. A. Miller (Washington U.), G. C. Duncan (Bowling Green State U.)
We present the results of 3-D relativistic jet simulations performed with a numerical hydrodynamic code employing a HLLE solver of Godunov-type and adaptive mesh refinement. Our goal is to explore the nature of flow structures that form, their evolution, and the extent to which a well-collimated relativistic flow persists when subject to significant perturbation. We conclude that, while relativistic flows were anticipated to be highly dissipative compared with non-relativistic flows, limiting their ability to preserve a well-collimated flux of energy and momentum in the presence of perturbations, a core of high momentum and energy flux is maintained even when the flow is subject to a large amplitude disturbance such as precession of the inflow. Specifically: a) an initially axisymmetric flow with no external perturbations exhibits instability comparable to that seen in corresponding 2-D simulations despite the larger number of available modes, because the increased thermalization associated with the increased number of degrees-of-freedom leads to a larger cocoon, reducing the impact of the contact surface instability on the jet; b) a jet impinging on an oblique density gradient -- an idealization of an ambient density inhomogeneity -- does not develop large amplitude internal structures, but does exhibit a strong tendency for the formation of very rarefied flow regions with strong (relativistic!) shear in the cocoon -- with significant implications for magnetic field topology and particle acceleration; c) a jet with precessing inflow develops large-scale high pressure and density (and thus high emissivity) structures within both jet and cocoon, but maintains a spine of high momentum flux (or `discharge'; \gamma2(e+p) vz2+p) that pushes forward a bow shock at almost 90% of the speed seen in the unprecessed case. This work was supported in part by NSF grant AST 9617032 and by the Ohio Supercomputer Center.
The author(s) of this abstract have provided an email address for comments about the abstract: hughes@astro.lsa.umich.edu