On the magnetic layer behind a shock wave

Abstract The growth in temperature behind a shock wave generates a sharp increase in the fluid conductivity. In the presence of a possible background magnetic field originating in the obstacle forming the bow shock, this creates a Lorentz force which acts upon the flow. Since this enhanced conductivity in hypersonic flows is limited to a narrow layer behind the shock, where also the density increases markedly, one is able to use some reasonable approximations to analyze the magnetohydrodynamic equations associated to the flow. This is performed in the plane and axisymmetric cases, with eminently intuitive results: the transverse component of the magnetic field acts as a brake, while the longitudinal component presses the streamlines against the body or separates them from it. Details for poloidal and toroidal fields are quite different.