Time evolution of the relative deviation | ΔB_z/ tanh(y_m) | of the magnetic field from the analytical prediction (top) and derived effective numerical resistivity η_n (bottom) at position (y_m,z_m) = (−0.5493,0) for the simulation of a Harris-like current sheet. Results for different spatial resolutions (number of grid points in y direction) are color-coded according to the legend. The high-frequency oscillations are caused by the mesh drift instability of the staggered leap-frog scheme, which is not explicitly damped in this simulation setup (cf. Sect. 2.2).