The Paris-Durham shock code simulates the propagation of a supersonic shock wave through a layer of gas. It calculates the dynamical, physical and chemical structure of the shocked layer.


At each point of the layer, the shock code solves the continuity equations on each side of the shock front with source terms, taking into account basic grain processes, chemical evolution and relevant exchanges between the different fluid components: neutral, ionized, and electronic. It hence resolves the dynamical structure of the gas (density, temperature and velocity of its components), as well as the chemical abundances for over 125 species linked by more than 1000 reactions. Also included in the shock model is the computation of the population of the levels of H2, the most abundant molecule, and an important cooling agent, collision, and reaction partner of the gas. The abundances of atoms and molecules of relevant species are calculated at each point, so a simple LVG model can be coupled to the shock model to compute their level populations, line emissivities, and integrated intensities, that can then be compared to the observations. Such an LVG model will soon be made available on this website.


The shock model can be used to study the physics and chemistry of:

  • dense clouds;
  • dense filaments (‘ridges’) hosting star formation;
  • jets and bipolar outflows associated to star formation;
  • shocks associated to old supernova remnants, typically interacting with nearby molecular clouds;
  • extra-Galactic shocks

Several works are in progress to improve this model:

  • implementing grain-grain interactions, V. Guillet, S. Anderl, A. Jones and G. Pineau des Forêts;
  • implementing self-consistent calculations of the cooling through CO, H2O, CH3OH and OH, D. R. Flower and G. Pineau des Forêts;
  • implementing the potential effect of a strong UV radiation field on the shock, B. Godard, P. Lesaffre and G. Pineau des Forets;
  • implementing pseudo 2D and 3D modelling, L. E. Kristensen, G. Pineau des Forêts, and S. Cabrit.;

The documentation describing the physics and chemistry implemented in the current model is available on the website. It also contains a list of references providing more details on the shock model, examples of studies based on its use, as well as references on the work in progress.