Instability of an initial dipole with Re = 2 × 10⁴ and Lu_p = 1000 (to have the same initial poloidal energy as the reference case with Lu_p = 100). Panel a): initial velocity (colours) and magnetic field lines (contours). Panel c): volume rendering of the instability. Panels b) and d): same as Fig. 7 for Ω₀/ω_Aφ0 = 5 and m = 4 (panel b)) and m = 7 (panel d)). Velocity is given in units of Re.