Growth rates of unstable modes for different amplitudes of the azimuthal magnetic field for a dust-free disk with ϵ = 0 (top panel), a dust-poor disk with ϵ = 0.2 (middle panel), and a dust-rich disk with ϵ = 3. The Stokes number was fixed to St = 0.1 and the ambipolar Elsasser number to Λ_AD = 100. The solid line corresponds to the RDI condition for the streaming instability (Eq. (26)), while the dashed black line corresponds to the RDI condition between Alfvén waves and the dust-gas radial drift (Eq. (29)). The dashed blue line corresponds to the condition for AD-modified Alfvén wave RDI (Eq. (39)).