Evolution of Kelvin-Helmholtz instabilities in radiative jets II. Shock structure and entrainment properties

We present the results of a 2-D numerical analysis of the stability of radiative supersonic cylindrical jets against Kelvin-Helmholtz instabilities. The numerical scheme employed is a PPM-type code, the boundary conditions are periodic on the longitudinal direction, i.e we adopt a temporal approach; the interface between the jet and the ambient medium is modeled by a smooth velocity and density transition. The equilibrium configuration is perturbed by a superposition of axisymmetric longitudinally periodic transverse velocity disturbances. We discuss the physical details of the temporal evolution of the instability when affected by non-equilibrium radiative losses in comparison with the adiabatic case for a perfect gas equation of state. We find that radiation strongly affects the instability evolution by limiting the mixing and momentum transfer processes between the jet and the ambient medium, depending mainly on the choice of the initial jet density. Our results are relevant for interpreting the phenomenology of YSO jets.