Fluid Dynamical Mechanisms for Knots in Astrophysical Jets
In Numerical Astrophysics, 88-126, ed. J. Centrella, J. LeBlanc, and R. Bowers (Jones and Bartlett: Boston), with K.-H. Winkler and M. Norman. (1985).
Abstract
Knotty jets recently discovered in a number of both young and evolved stellar systems show remarkable similarities in appearance to knotty extragalactic jets of vastly larger dimensions. In every case, knot emission in stellar jets is found to be shock-excited, which is strongly suspected to be the case in extragalactic jets as well (e.g. M87). We argue that fluid-dynamical instabilities (pinching and kinking) grow to nonlinear amplitude in knotty astrophysical jets and produce large-scale shock systems of the strength and distribution necessary to yield the observed knots. The behavior of fluid instabilities in the nonlinear regime and their saturation through shock formation is demonstrated by 2-dimensional gas dynamical simulations.