Magnetic-field lines disconnected from BH horizon within r < 6M in the retrograde a = −0.9 case at the peak of BH magnetic flux during the onset of magnetic flux eruption (t = 17 050M; cf. Fig. 2), with lines colored by the magnetization parameter σ = b²/w. A sample of doubly connected lines is shown in white. The small magenta patches mark regions of relativistic temperature (log₁₀T ≥ 0.5). The viewpoint is at θ_obs = 0° , with ϕ measured counterclockwise from the right. The black sphere indicates the outer horizon at r_H = 1.436M. The grid of black arcs marks the radii r/M = 2, 3, 4, 5, 6 in the equatorial plane θ = 90°. An associated movie is available online.