Time evolution of the maximum ρ_d∕ρ_g. The back reaction to v_r is included in the results in panel b, but not in panel a. The light blue, magenta, blue, green, and red curves are the results with F_p/g = 0.025, 0.05, 0.1, 0.2, 0.4, and 0.8, respectively. The other parameters are fixed as α_acc = 10⁻² and Δx_subl = 0.1H_g and Δz_subl = 0.03H_g. To mimic the settings of Ida & Guillot (2016), we artificiallly set α_Dr = 0, α_{D z} = 10⁻⁵ and τ_s,d = 10⁻² (however, the relatively large τ_s,d for the silicate dust is not reflected to the dust drift speed). The latter two parameters maintain H_d = Δz_subl. The circles in panel a represent the analytical solution given by Eq. (31). That in panel b is the analytical solution for non-divergent case (F_p/g = 0.025) given by Eq. (15).