Drift velocity through the shock front for the simulation with β = 0.3 and ξ_i = 0.01. The x-axis is shifted by x_s, where x_s is taken as the point in the shock where the drift velocity is at its peak, so that both distributions are aligned. It is clear that the distribution of the drift velocities is the same at both times indicating that the shock front has reached a steady state. The reference time is taken at t₀ = 120 000τ.