Evolution of magnetic energy spectra for Runs A–D shown in time intervals ﹩{\rm{\Delta }}t﹩ with ﹩{\rm{\Delta }}t\,\eta {\mu }^{2}=6﹩ until ﹩t\,\eta {\mu }^{2}=80﹩ (marked in blue) followed by longer time intervals that increase by a factor of two. The vertical dashed line marks the wavenumber ﹩k={\mu }_{0}/2﹩ where the growth rate is maximum. The horizontal dotted line marks the level of ﹩{C}_{\mu }\overline{\rho }{\mu }_{0}{\eta }^{2}﹩, and the horizontal dashed–dotted line marks the level of ﹩{C}_{\lambda }{\mu }_{0}/\lambda ﹩. The red lines have slopes of −2 and +4. Panel (d) corresponds to regime II, while panels (a) and (b) correspond to regime I.