Test-particle analysis of a planar and rippled shock. Top: reduced distribution f(x, v_x) of ions obtained with a test-particle analysis in a planar shock. The solid black line shows the magnetic field profile. The arrow points to the backstreaming ions. Bottom: reduced distribution f(x, v_x) of ions obtained with a test-particle analysis in a rippled shock. The magnetic profile is represented by a ribbon because each ion measures its magnetic field magnitude along its path.