Top view of the rest-mass density of P1U4, along with the field lines at T_A = 0 (left panel) and near to the end of the simulation (≈12.5T_A). The color bar (logarithmic scale) ranges from the atmospheric density to the maximum rest-mass density at the corresponding time. The black and gray rectangles to the left of the color bar indicate opacity, which ranges from fully opaque (black) to ∼76% opacity (gray).