a) Longitudinal perturbations v_y for η = 0.01, β = 0.1 plasma comparing η = 0.01, ν = 0 (blue) and ν = 0.01, η = 0 (red). Note only 0 ≤ y ≤ 350 is shown and that the agreement after y ≈ 280 is excellent (the two curves lie on each other). b) Blow-up of v_y over region 0 ≤ y ≤ 100 for ν = 0.01, η = 0 plasma only, where crosses indicate grid point resolution. Black line indicates v_y = 0. In both subfigures, t = 1000τ_A.