The compression of a magnetic field by a shock in a predominantly neutral gas is discussed. By solving the fluid equations, a steady-state structure is determined for a one-dimensional shock front propagating through a partially ionized gas in a direction perpendicular to the field lines. Temperatures and velocities of ions, electrons, and atoms are calculated as a function of the spatial coordinate moving with the shock frame. When the degree of ionization is small, field compression occurs at the expense of the momentum carried by the neutral atoms. The neutral momentum is transferred indirectly to the field by way of the ions. To effect the transfer, many ion–atom collisions are required. Shock widths from several hundred to several times 10 4 ion–atom mean free paths are required. Within the broad profile, a narrow atom shock is imbedded near the hot end if the shock speed exceeds a critical value.
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D. J. Mullan (1971) studied this question.