Selected magnetic field lines within r ≤ 6M in prograde a = 0.9 case at onset of magnetic flux eruption (t = 19 594M), colored by the magnetization parameter σ = b²/w (line colors are also affected by shading, with lines seen at small angles rendered darker). Upper panel: Horizon-connected lines seeded at r₀ = 5.9M for θ_L3, min < θ₀ < 90°, seen from latitude θ_obs = 135°; lower panel: horizon-disconnected lines seeded at r₀ = 5.9M for θ_L3, min < θ₀ < θ_L3, max, seen from latitude θ_obs = 45°. In both panels, a small but (θ₀, ϕ₀)-complete sample of doubly connected lines (closed loops with max(r) < 6M) seeded at r₀ = 1.42M (just under the horizon) are shown colored in white. Both images are seen from the same azimuth ϕ_obs = 180°; data for 150° < ϕ < 210° (except for the doubly connected lines) are cut out to reveal (r, θ) sections. Black spheres indicate the outer horizon at r_H = 1.436M. The grid of arcs marks the radii r/M = 2, 3, 4, 5, 6 in the equatorial plane θ = 90° (gray) and in the ϕ = 90° quadrant spanning the latitudes θ_L3, min ≤ θ ≤ θ_L3, max (black). A small magenta patch just to the left of the horizon marks relativistic temperature (log₁₀T ≥ 0.5). An associated movie is available online.