Schematic view of current filamentation and coalescence in a knotty region. When plasmoids ejected intermittently from the central engine catch up with the preceding flow, the bulk breaks up into numerous separate fragments. The filaments are represented by many pipes; the inset illustrates a sample of the realistic one that is bent or twisted. The filaments soon coalesce due to the attractive force acting on the currents in the same direction. These processes actively repeat because of multiple shocks. The corresponding spectra of turbulent magnetic fields are depicted on the right side. The filamentation is driven at the scale of plasma skin depth (c/ω_p), and the magnetic-field energy accumulates on the largest scale (D) via the inverse cascade in the k space (left-pointing arrow).