Time-dependence of the maximum of the magnetic field (left panel), the location of the singular points (middle panel; upper curve for ℒ(t), lower curve for ℒ_cs(t)), and the value of the integral ∫B(x, t) dx in the central lobe of the solution (right panel) for the solution of the first harmonic, illustrated in Fig. 4. The Bifrost solution is shown as a solid black line and the theoretical solutions as dashed red lines.