Temporal evolution of a BMR from case 1 at selected temporal points (a) t = 0 days, (b) t = 2.1 days, and (c) t = 6.4 days. The kinematic simulation with the same initial condition is shown in panel (d) at t = 6.4 days. Top panels show the radial field B_r at the surface r = 0.985 R_⊙. Thick black solid curves show the contours at |B_r| = 0.3 kG. The blue and red cross marks represent the locations of the flux-weighted center for the leading and following spots, and the grey straight lines are drawn to connect these two cross marks. Middle panels show the radial flows, v_r, near the surface, r = 0.98 R_⊙, by colored contour and the horizontal velocities (v_θ, v_ϕ) at the surface by vector arrows. Bottom panels show cross sections of the magnetic field strength |B| at the fixed latitude of 20°, denoted by black dashed lines in the top and middle panels.