AAS 201st Meeting, January, 2003
Session 86. Radio Galaxies and Jets
Poster, Wednesday, January 8, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[86.12] Poynting-flux-dominated Jets in Decreasing Density Atmospheres

M. Nakamura, D. L. Meier (Jet Propulsion Laboratory)

We present 3-dimensional MHD simulations of Poynting-flux-dominated (PFD) jets that are generated by the "Sweeping-Magnetic-Twist Mechanism" of jet production. Our study focuses on the stability of the non-linear torsional Alfvén wave train (TAWT) and the development of current-driven helical instabilities, which may be responsible for the "wiggled" structure seen in AGN jets. Our previous numerical results (Nakamura et al. 2001) had revealed that PFD jets would be subject to the kink mode (m=1) helical instability when the jet experiences a decreasing Alfvén velocity distribution caused by an {\em increasing} ambient density.

In the present study we investigate the behavior of jets in a variety of more realistic galactic atmospheric conditions, including decreasing density, pressure, and temperature gradients. We find that PFD jets can develop helical-kink distortions even when the jet experiences decreasing ambient conditions {\em and} the flow is strongly magnetically dominated. Nevertheless, some of our jets are apparently stable for the duration of the simulation, and we shall discuss possible criteria for MHD jet stability. MN is supported by NRC.

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