Flux function as a function of the horizontal position at z = 0. The continuous line corresponds to the Gaussian profile, and the dotted line shows the parabolic profile. The horizontal dashed lines represent the constant values that the Gaussian profile tends to asymptotically. In this plot, w₀/h = 1, and C = 0 for the Gaussian profile, while x₀/h = 1 for the parabolic profile.