Top: normalized shortest growth time of gravitationally unstable mode () as a function of normalized mass-to-flux ratio (μ₀). Bottom: normalized preferred length scale of the most unstable mode () as a function of the normalized mass-to-flux ratio (μ₀). Each panel shows curves for models (as shown in Eq. (4)) with normalized neutral–ion collision time (black), 0.001 (red), 0.04 (blue), and 0.2 (green). Here, represents the flux-frozen case as a reference. The Toomre-Q rotation parameter and the dimensionless ohmic diffusivity are set to be zero. As the degree of ambipolar diffusion (i.e., ) increases, the growth timescale and length scale become shorter (see Ciolek & Basu 2006; Bailey & Basu 2012; Das & Basu 2021) for further details.