Volume-averaged magnetic energy density, E_mag, for the ideal-MHD simulations sg-mhd-2 (black), sg-mhd-tau10 (red), and sg-mhd-tau20 (blue) and the resistive simulation sg-eta01 (cyan). The time axis starts at t = 0 for all simulations. For the ideal-MHD runs, this corresponds to the moment of field seeding and for the resistive run, (t = 0) corresponds to the moment when resistivity was introduced. The dashed black lines correspond to linear fits, according to the values in Table 5.