Graphical estimation of numerical resistivity (top panel) and numerical viscosity (bottom panel). Each dot represents the maximum magnetic field (B_max) or velocity (V_max) obtained from a simulation with a specific explicit value of η or ν. The blue solid line is a fit to these data points. Two horizontal lines are shown: one corresponds to the B_max/V_max value for the case with η = 0 and ν = 0, and the other marks the threshold of numerical noise. The intersection of this threshold with the fitted curve defines the estimated numerical resistivity or viscosity, indicated by the vertical line.