Normalized reduced χ² value (ϵ_x) was calculated for the two fitting combinations to decide the goodness of a fit, that is, which combination of functions would fit the flow maps better. Panels a and b: distribution for the difference between ϵ₁ and ϵ₂, for the distributions obtained from the LOS magnetograms, as well as for the difference between ϵ₃ and ϵ₄, for the distributions obtained from the continuum maps. Normalized reduced chi squared values ϵ₁ and ϵ₃ are related to Eq. (4), whereas ϵ₂ and ϵ₄ are related to Eq. (5). Panels c and d: temporal evolution of the changes of these differences between corresponding ϵ.