Magnetic Fields and Free-Free Emission

The magnetic field is plotted against the preshock density for three different shock velocities. Above the dotted line, the magnetic field is so strong that no shock occurs. The shaded area between the dotted line and the points indicates the region of parameter space where the magnetic field reduces the observed flux with respect to the nonmagnetic case by at least 20%. Dashed lines denote comstant magnetosonic Mach numbers.