Vertical component of magnetic field (top row), H_α wing intensity (middle row), and field topology (bottom row) at t = 112,197, and 549 s from left to right. The colour-coding of the field lines in the bottom panels corresponds to the vertical velocity with upflows being blue. Horizontal planes show the vertical component of the magnetic field at the surface. The magnetograms are cropped at ± 1 kG and normalized H_α-wing intensity at 0.7 to 4.5.