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'; γ 2(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.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1999