Influence of magnetic fields on pulsed, radiative jets

Abstract

We present results of magnetohydrodynamic simulations of steady and time variable jets for a set of conditions applicable to outflows from young stellar objects (YSOs). As a first step in a detailed study of radiative magnetohydrodynamic jets, we study both steady and pulsed jets with a large-scale magnetic field oriented parallel to the jet flow axis. While toroidal components may be present in many jets, we have chosen in this initial study to focus solely on pure poloidal initial geometries. The range of magnetic field strengths studied is characterized by the dimensionless parameter beta = 8 pi P-gas/B-2 = 0.1-10(7). The results of our simulations show that the global characteristics are not strongly dependent on the strength of the magnetic field. Instead, we find that a predominantly poloidal field has more subtle effects, such as inhibiting instabilities, and increasing the "order" in the flow patterns. While the fields act to restrict "turbulent" gas motions, the pulse-induced internal shocks increase the likelihood of instabilities, complicate the global flow patterns, and increase the likelihood of magnetic reconnection. We detail the ways in which the magnetic pressure and tension forces affect the kinematics observed in these simulations