Numerical results (lines) of the growth rate σ as a function of k_z for various parameter sets of : (1,1) (black, Ω = 0.707 and θ = 45°), (1,2) (blue, Ω = 1.118 and θ = 63.4°), (1,3) (red, Ω = 1.581 and θ = 71.6°), (−0.5, 1) (green, Ω = 0.559 and θ = 116.6°), (−1, 1) (yellow, Ω = 0.707 and θ = 135°), at Pe = 0.1, k_x = 0, N = 1, and Re = ∞, and asymptotic results (circles) from Eq. (79) in the limit Pe → 0.