Magnetohydrodynamic turbulent mixing layers: Equilibrium cooling models

We present models of turbulent mixing at the boundaries between hot ( T similar to 10(6) - 10(7) K) and warm material ( T similar to 10(4) K) in the interstellar medium, using a three-dimensional magnetohydrodynamic code, with radiative cooling. The source of turbulence in our simulations is a Kelvin-Helmholtz instability, produced by shear between the two media. We find that because the growth rate of the large-scale modes in the instability is rather slow, it takes a significant amount of time ( similar to 1 Myr) for turbulence to produce effective mixing. We also find that the total column densities of the highly ionized species (C IV, N V, and O VI) per interface ( assuming ionization equilibrium) are similar to previous steady state nonequilibrium ionization models but grow slowly from log N similar to 10(11) to a few; 10(12) cm(-2) as the interface evolves. However, the column density ratios can differ significantly from previous estimates, with an order of magnitude variation in N(C IV)/N(O VI) as the mixing develops.