Heating and ionization in MHD switch-on shocks in partially ionized plasmas

The structure of MHD switch-on shocks propagating along a magnetic field into an upstream partially ionized plasma is studied experimentally and theoretically. Detailed measurements of density, temperature and magnetic field are presented, and compared with a model based on the fluid equations for electrons, ions and neutral atoms. The main feature of the model is that dissipation of shock energy occurs primarily through ion collisions with neutrals. According to the model, at low upstream ionization levels, ions and neutrals are preferentially heated above the electrons. At high ionization levels, the electrons are more strongly heated. This is found to be in agreement with the shock structures obtained for 4 switch-on shocks, differing in the level of upstream ionization. (author)