Time evolution of the magnetic field (left panel) and timescale of reacceleration (right panel) from z = 0.3 to 0.1 along the trajectories of N = 5.1 × 10⁵ tracer particles that end up in the bridge region (white box in Fig. 1). In both panels, the solid line and the shaded region show the median value and 1σ range of the distribution. In the left panel, the red and blue lines show the dynamo magnetic field calculated with η_B = 0.05 and the original magnetic field in the Enzo simulation, respectively. The dashed and dotted lines show the median values for different parameters.