Emission line ratios from variable velocity jet models

In this paper we present a grid of axisymmetric numerical simulations of variable ejection velocity jets. In these models we assume that the jets are ejected with a sinusoidally varying ejection velocity and a time-independent ejection density. The grid of models then spans a range of different velocity variability amplitudes and periods. Because the simulations include a treatment of the non-equilibrium ionization state of the gas, we are able to make predictions of the emission in a set of different emission lines. In this way, we obtain predicted emission line ratios for the successive knots along the jets (which correspond to the "internal working surfaces" formed as a result of the ejection velocity variability), which can be compared directly with observations of the chains of knots along HH jets.