Same test as in Fig. B.1, but with an additional level of mesh refinement for x ≤ −0.25. Left: comparison of global charge conservation between a uniform grid (red line), a refined mesh with refluxing (blue line), and a refined grid without refluxing (black line). We display the relative deviation of the total charge from its initial value for different setups. Right: difference between the electromagnetic energy density for the refined mesh with and without refluxing at t = 2.0.