Distributions of vertical magnetic field strength (B_z; panel a), horizontal magnetic field strength (B_h; panel b), inclination angle (angle; panel c), and vertical current density (J_z; panel d) on the plane z = 0.2 at t = 144 t_A (first column), t = 164 t_A (second column), and t = 184 t_A (third column) in “Simulation 1”. The red dashed or solid contour in each sub-panel shows the outline of the footprint of QSLs in this plane, in which logQ ≥ 3. The orange or blue dashed line in each sub-panel marks the slit crossing through the sunspot scar, whose 1D plots are shown in Fig. 9. A movie of this figure is available online.