Solution of the 1.75D shock tube problem at time t = 0.5. Top row: MHD reference result with different resolutions: 800 points (dashed red), 4096 points (solid light blue), 8192 points (solid dark blue), 16384 points (dashed black). Bottom row: two-fluid model for different values of the collisional parameter: α = 10² (solid orange), α = 10⁴ (solid red), α = 10⁸ (solid light blue) and α = 10⁶⁴ (dashed dark blue). The reference MHD solution is also shown with a dotted black line. Left columns: density. For the two-fluid case in the bottom left panel, the sum of densities of neutrals and charges is shown. Right columns: B_y