Demo · Physics & Geometry

Reconnection vs. BZ: Which Channel Wins?

Three tools trace the two parallel energy extraction channels from OC’s Kerr IMBH — and show when plasmoid reconnection overtakes the Blandford-Znajek jet.

3 tools · ~10 min · Meringolo et al. 2025
⚙ Choose a spin regime

Each scenario pre-loads all three tools with the spin parameter that defines which extraction channel dominates. Walk the chain to see how the balance shifts.

01
Step 1 · Spacetime Structure
The Ergosphere Boundary

The Blandford-Znajek mechanism and magnetic reconnection both operate in or near the ergosphere — the region outside the event horizon where spacetime rotation is compulsory. At a★ = 0.95, the ergosphere at the equator extends to 1.63 rg vs the event horizon at 1.31 rg. The reconnection layer forms at the ergosphere boundary itself, driven by the differential rotation of field lines. At a★ = 0.7, the ergosphere shrinks to ≈1.86 rg and the event horizon sits at 1.71 rg — a much thinner ergospheric shell, with correspondingly weaker differential rotation. The geometry of the ergosphere is the first variable in the energy budget.

Open Kerr Geometry Viewer → a=0.95 · M = 8,200 M⚁ GR exact
Step payoff
The ergosphere extent and the gap between horizon and ergosphere set the physical volume available to both extraction channels. A thicker ergosphere means more room for reconnection.
02
Step 2 · BZ Jet Power
The Blandford-Znajek Baseline

The BZ mechanism extracts rotational energy via the interaction of magnetic field lines threading the horizon with the frame-dragging of the Kerr spacetime. Power scales as P_BZ ∝ a★² × B² × M². At a★ = 0.95 and B = 10&sup6; T: P_BZ ≈ 3.8×10³⁵ W (Scenario A). At a★ = 0.7: P_BZ ≈ 9.2×10³⁴ W (Scenario B). This is the baseline all other channels are compared against. The BZ power is the dominant channel at all spin values — reconnection adds fractionally on top of it. The power ratio between the two spin values is approximately 4:1, reflecting the a★² dependence.

Open BZ Calculator → mass=8,200 M☉ · spin=0.95 · B=10⁶ T Blandford-Znajek 1977
Step payoff
The BZ mechanism provides the dominant power floor. The reconnection channel is the correction term — but at near-maximal spin, it is a correction term that cannot be ignored in precision energy budgets.
03
Step 3 · Reconnection Channel
When Plasmoids Add Power

Meringolo, Camilloni & Rezzolla (2025, ApJL 992, L8) ran GRPIC simulations of Kerr magnetospheres and found that plasmoid instabilities in the ergosphere drive a second extraction channel. At a★ = 0.95, reconnection adds ~18% to total BZ power (Prec ≈ 6.8×10³⁴ W). At a★ = 0.7, the contribution drops to ~4%. The reconnection layer is physically distinct from the BZ circuit — it operates at the ergosphere boundary, not the horizon. The reconnection efficiency ηrec is calibrated to GRPIC simulation results at ηrec = 0.15. A key result from the simulations: reconnection power scales more steeply with spin than BZ, approximately as a★³, meaning the gap between the two channels narrows rapidly as spin approaches unity.

Open Reconnection Calculator → ηrec = 0.15 · B = 10&sup6; T · M = 8,200 M⚁ Meringolo 2025 GRPIC
Step payoff
The reconnection channel is not a rounding error at near-maximal spin. It adds ~18% to total power in Scenario A — and because it scales as a★³, spinning the IMBH from 0.7 to 0.95 triples the reconnection contribution while only doubling the BZ baseline.
⚖ Combined Channel Budget

At a★ = 0.95 (Scenario A), the combined BZ + reconnection power is Ptotal ≈ 4.5×10³⁵ W — Kardashev K ≈ 2.45. Reconnection contributes ~18% but cannot be ignored in precision energy budgets. The critical insight: reconnection power scales more steeply with spin than BZ (Prec ∝ a★³ approximately), so near-maximal spin is dramatically more efficient.

Spinning the IMBH from a★ = 0.7 to 0.95 roughly doubles BZ power but triples total extraction power. This is the physical argument for why Phase 1 targets near-maximal spin rather than stopping at a★ = 0.7: the final 35% of the spin-up journey delivers a disproportionate energy payoff, with reconnection accounting for an increasing share.

For the spin-up timeline that quantifies how long Phase 1 takes, see Demo — Spin-Up Economics. For the full MTH energy extraction sequence from capture to Kardashev II, see the BH Energy Budget Workflow.

EPISTEMIC TIERS: Established = peer-reviewed physics within the standard formulation. Debated = active disagreement in the published literature. Theoretical = published framework, awaiting decisive observation.