Extended Data Fig. 2: Cascade of kinetic and magnetic energies from large scales to small scales.
Nonlinear energy flux through spectral space is measured in a simulation with 4096 × 4096 × 8192 grid points. Here, \(k={({k}_{x}^{2}+{k}_{y}^{2})}^{1/2}\). The energy flux is integrated over the z-axis. A constant energy flux in k-space indicates an inertial range. Energy injected externally to the mean flow (shown with a white-headed arrow on the left margin) is cascaded to small scales, as shown by \(\Pi \)uu, which measures energy flux due to transfer of energy between two velocity fluctuations. Magnetic-to-magnetic energy flux \(\Pi \)bb shows a prominent small-scale cascade over two decades of inertial range. This analysis shows that the ϒ-dynamo arising in KH-unstable shear flow is not due to an inverse cascade of energy. The ϒ-dynamo is due to energy transfer from large-scale jets to the mean field, as demonstrated in Extended Data Fig. 3.
