Time evolution of B_z at the τ = 1 level in the photosphere. We present snapshots at t = 16, 24, 28, 30, 32, 40, 70, and 140 hr. For comparison, the flux emergence process at the bottom boundary is finished at t = 19.33 hr, the transition to an open boundary condition at t = 22.1 hr.

(An animation of this figure is available in the online journal.)

The video/animation of this figure is available in the online journal.