Structure and Stability of Keplerian Magnetohydrodynamic Jets

Abstract

MHD jet equilibria that depend on source properties are obtained using a simplified model for stationary, axisymmetric and rotating magnetized outflows (Lery et al. Lery et al. 1998,Lery et al. 1999a). The present rotation laws are more complex than previously considered and include a Keplerian disc. The ensuing jets have a dense, current-carrying central core surrounded by an outer collar with a return current. The intermediate part of the jet is almost current-free and is magnetically dominated. Most of the momentum is located around the axis in the dense core and this region is likely to dominate the dynamics of the jet. We address the linear stability and the non-linear development of instabilities for our models using both analytical and 2.5-D numerical simulation's. The instabilities seen in the simulations develop with a wavelength and growth time that are well matched by the stability analysis. The modes explored in this work may provide a natural explanation for knots observed in astrophysical jets.

Proper motions and velocity asymmetries in the RW Aur jet

“…Adopting as the jet characteristic radius r j half the FWHM measured at the same distances in Paper II, the inner knot spacing is then ∆x 8-10 r j . For comparison, the axisymmetric pinch instabilities in MHD jets simulated by Lery et al (2000) produce jet knot spacings of ∆x/r j ≤ 3, while Kelvin-Helmholtz instabilities predict ∆x/r j V j /c s > 10. An even more important observational constraint is that the first moving knot appears at a distance d min < ∆x, while the growth scale of an instability is expected to be several times its wavelength.…”

Particle acceleration in rotating and shearing jets from AGN

“…Camenzind 1996;Fendt 1997a), while more generally differential rotation would be intuitively expected if there is an intrinsic connection between jet motion and the rotating disk (cf. also Fendt 1997b; Lery & Frank 2000).…”

Curved Herbig‐Haro Jets: Simulations and Experiments

“…The simulations show the development of the RTI in curved jets and how it may be partially quenched by rotation, which rapidly shears the RT modes. To determine the observational signatures of such an effect and for direct comparison to observation, more realistic angular velocity profiles need to be used (see, for example, Lery & Frank 2000).…”