Black hole Limits Redefined: Extreme Efficiency in Black Hole Jets

TL;DR

This paper uses advanced GRMHD simulations to demonstrate that black hole jets can achieve efficiencies over 100 times greater than accretion energy, challenging traditional limits and offering new insights into black hole energy extraction.

Contribution

It introduces a novel simulation regime where accretion is suppressed and jet power vastly exceeds accretion energy, revealing unprecedented efficiency levels in black hole jets.

Findings

Jet power exceeds accretion energy by over two orders of magnitude

Accretion can be globally suppressed in a magnetically arrested disk state

Results challenge traditional limits of black hole energy extraction

Abstract

Relativistic jets from black holes can extract energy not only from accretion but also directly from the black hole's spin, as described by the Blandford-Znajek mechanism. A longstanding question is whether magnetic flux can accumulate near the event horizon to such an extent that it halts accretion entirely, enabling energy extraction purely from spin. Previous studies have shown that accretion persists through instabilities and that jet power only modestly exceeds the accretion energy budget, yet some observational results suggest much higher efficiencies. Here we present state-of-the-art general relativistic magnetohydrodynamic (GRMHD) simulations that sustain a quasi-steady magnetically arrested disk state for approximately 10,000 dynamical times, during which accretion is globally suppressed across the full azimuthal extent. In this regime, jet power exceeds the accretion energy input by more than two orders of magnitude, demonstrating a previously unachieved level of efficiency. These results challenge conventional assumptions about the limits of black hole energy extraction and suggest a new framework for interpreting powerful jet systems. Our findings raise important questions about the long-term stability of such states and the fundamental limits of the Blandford-Znajek process.