Force ratio F_Ph∕F_D. The solid lines correspond to the force ratio calculated from the normal model, and the dashed lines are the dust-poor model. The vertical lines represent the location of the light barrier. The line colors represent the value of α for the outer region (α = 10⁻³ for pink, α = 5 × 10⁻⁴ for orange, and α = 2.5 × 10⁻⁴ for blue). Weassume that the value of α for the inner region is ten times higher than that for the outer region, and the mass accretion rate is Ṁ = 10⁻⁸M_J yr⁻¹.