Temporal evolution of the magnetic energy E_mag (black lines) and of the poloidal kinetic energy (red lines) in five unstratified axisymmetric runs at different Re and Ha₀ (see the legend at the top). The magnetic Prandtl number Pm is 1. Time is scaled with the viscous diffusion time τ_ν here. Note that the left and right vertical axes span different ranges. The gray line displays the exponential Ohmic decay rate based on for the run at Re = 5 × 10⁴ and Ha₀ = 4 × 10³ (see the main text for details).