Azimuthally-averaged toroidal field and meridional cut of the fluctuating radial field during the growing phase of the instability for cases where Re = 2 × 10⁴ and Lu_p = 60 (left panels) and with Re = 4 × 10⁴ and Lu_p = 120 (right panels). In the northern hemisphere and for each snapshot, the contours of the growth rate for m = 5 and Ω₀/ω_Aφ0 = 5 predicted by the linear analysis are superimposed to the colour contours.