Case 7, Convergence Study: B(z) = 0, A = 2 * π * α for α = 10³. Here we use the loglog plot of the maximum error = |det(∇ x) - 1| vs the number of the grid size nx=129, 257, 513, 1025, 2049 in order to estimate the order of the convergence for each integration time T = 3, 4.5 and 6 days.