An analysis is presented of the equations of motion for steady magnetohydrodynamic (MHD) shock waves propagating in interstellar clouds, for boundary conditions that preclude C shocks. In addition to J shocks, in which the neutral fluid component becomes subsonic at an adiabatic jump front, the equations admit a new class of solutions called C* shocks, in which the transition to subsonic flow occurs continuously at a sonic point. Numerical methods are developed for computing the structure of J and C* shocks propagating in diffuse interstellar clouds; the effects of chemical, ionization, and recombination processes are included in this treatment. An alternative numerical method, which uses "artificial viscosity" to facilitate integration through sonic points, is analyzed and shown to be invalid. A set of exemplary solutions, computed for realistic shock parameters, shows that C* shocks occur for a broad range of conditions relevant to diffuse interstellar clouds.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
- Interstellar: matter
- Shock waves