Normalized growth rate γ of the m = 1 mode (energy of B_r). a) The initial magnetic field is as in Eq. (6), n = 0,Ω_A0 = 2 and the rotation Ω₀ is varied as to change w = Ω_A0/Ω₀. b) The dotted line is , c) the dot-dashed line γ = Ω_A0.8, and d)–f) show γ for various degrees of differential rotation. The asterisk denotes a case where the angular velocity was initially increasing outwards (see Sect. 3.2).