A New Solution to the Plasma Starved Event Horizon Magnetosphere: Application to the Forked Jet in M87

TL;DR

This paper proposes a new model for the event horizon magnetosphere in low luminosity black hole systems, explaining the observed hollow, weak jets in M87 and challenging previous assumptions about jet power and magnetic flux accumulation.

Contribution

It introduces a novel EHM model where weak poloidal magnetic flux leads to dissipation rather than flux accumulation, explaining the weak, hollow jets observed in M87.

Findings

Hollow jets in M87 are powered by inner accretion flow with intrinsic power.

The new EHM model predicts less poloidal flux and jet power than previous models.

The model explains the observed jet morphology and spectral features.

Abstract

Very Long Baseline Interferometry observations at 86 GHz reveal an almost hollow jet in M87 with a forked morphology. The detailed analysis presented here indicates that the spectral luminosity of the central spine of the jet in M87 is a few percent of that of the surrounding hollow jet $200 -400 \mu\rm{as}$ from the central black hole. Furthermore, recent jet models in indicate that a hollow "tubular" jet can explain a wide range of plausible broadband spectra originating from jetted plasma located within $\sim 30\mu\rm{as}$ of the central black hole, including the 230 GHz correlated flux detected by the Event Horizon Telescope. Most importantly, these hollow jets from the inner accretion flow have an intrinsic power capable of energizing the global jet out to kiloparsec scales. Thus motivated, this paper considers new models of the event horizon magnetosphere (EHM) in low luminosity accretion systems. Contrary to some models, the spine is not an invisible powerful jet. It is an intrinsically weak jet. In the new EHM solution, the accreted poloidal magnetic flux is weak and the background photon field is weak. It is shown how this accretion scenario naturally results in the dissipation of the accreted poloidal magnetic flux in the EHM not the accumulation of poloidal flux required for a powerful jet. The new solution indicates less large scale poloidal magnetic flux (and jet power) in the EHM than in the surrounding accretion flow and cannot support significant EHM driven jets.