in press in the Astrophysical Journal
We compute the nonlinear development of the instabilities in C-shocks first described by Wardle, using a version of the ZEUS code modified to include a semi-implicit treatment of ambipolar diffusion. We find that, in three dimensions, thin sheets parallel to the shock velocity and perpendicular to the magnetic field lines form. High resolution, two-dimensional models show that the sheets are confined by the Brandenburg & Zweibel ambipolar diffusion singularity, forcing them to numerically unresolvable thinness. Hot and cold regions form around these filaments, disrupting the uniform temperature structure characteristic of a steady-state C-shock. This filamentary region steadily grows as the shock progresses. We compare steady-state to unstable C-shocks, showing excitation diagrams, line ratios, and line profiles for molecular hydrogen lines visible in the K-band, with the Infrared Space Observatory, and with NICMOS on the Hubble Space Telescope.
Postscript and jpegs from astro-ph
Individual postscript files (6.5 Mb total):
Figures: 1, 2, 3, 4a, 4b, 4c, 5, 6, 7, 8, 9a, 9b, 10, 11, 12, 13a, 13b, 14, 15, 16, 17, 18, 19.
MPI Astronomie theory group