Growth rate of the CFI as a function of axial wavenumber kR_c, computed using the profiles for simulation A_0.1 presented in Fig. 5. Shaded vertical bands indicate the values of kR_c corresponding to azimuthal mode numbers m = 1 to m > 6, derived from the simulation jet radius R_j = 0.08 and local curvature radius R_c = 15.28. The most unstable mode occurs at k_maxR_c ≈ 190, in agreement with the effective kR_c from the simulation for m = 1.