ELECTRON TEMPERATURE EFFECTS IN FAST MAGNETOHYDRODYNAMIC SHOCK WAVES

The interaction between magnetic and electron temperature effects is analyzed in the simplest nontrivial case of fast magnetohydrodynamic shock waves in a slightly ionized plasma. This inter-action occurs because the magnetic structure and the associated Joule heating are dependent on the variation of electrical conductivity; the latter is affected by the electron temperature structure which depends in turn on the amount of Joule heating in the magnetic layer. The ionization is assumed to be frozen and so slight that the heavy particle structure (including a viscous subshock) is independent of that of the electrons. For negligible Hall currents a nonuniform coordinate stretching formally decouples the magnetic equation from the electron temperature system; the resulting two-point boundary-value problem is solved by matching asymptotic expansions in the outer magnetic layer and intermediate thermal layer when the respective length scales differ by a factor of about 3. The fine structure of the inner subshock region is not considered. Joule dissipation preheats the electrons in the upstream magnetic layer. Near the subshock the effect of a sudden compression of the electrons due to charge coupling with the heavy ions is diffused by thermal conduction, and there is a collisional relaxation zone downstream.