Evidence on the Origin of Ergospheric Disk Field Line Topology in Simulations of Black Hole Accretion

This Letter investigates the origin of the asymmetric magnetic field line geometry in the ergospheric disk (and the corresponding asymmetric powerful jet) in 3-D perfect magnetohydrodynamic (MHD) numerical simulations of a rapidly rotating black hole accretion system reported in \citet{pun10}. Understanding, why and how these unexpected asymmetric structures form is of practical interest because an ergospheric disk jet can boost the black hole driven jet power many-fold possibly resolving a fundamental disconnect between the energy flux estimates of powerful quasar jets and simulated jet power \citep{pun11}. The new 3-D simulations of \citet{bec09} that were run with basically the same code that was used in the simulation discussed in \citet{pun10} describe the "coronal mechanism" of accreting poliodal magnetic flux towards the event horizon. It was determined that reconnection in the inner accretion disk is a "necessary" component for this process. The coronal mechanism seems to naturally explain the asymmetric ergospheric disk field lines that were seen in the simulations. Using examples from the literature, it is discussed how apparently small changes in the reconnection geometry and rates can make enormous changes in the magnetospheric flux distribution and the resultant black hole driven jet power in a numerical simulation. Unfortunately, reconnection is a consequence of numerical diffusion and not a detailed (yet to be fully understood) physical mechanism in the existing suite of perfect MHD based numerical simulations. The implication is that there is presently great uncertainty in the flux distribution of astrophysical black hole magnetospheres and the resultant jet power.Comment: To appear in MNRAS Letter

The Jet Power and Emission Line Correlations of Radio Loud Optically Selected Quasars

In this Letter, the properties of the extended radio emission form SDSS DR7 quasars with $0.4<z<0.8$ is studied. This low redshift sample is useful since any corresponding FIRST radio observations are sensitive enough to detect extended flux in even the weakest FR II radio sources. In the sample, 2.7% of the sources have detectable extended emission on larger than galactic scales ($>$ 20 - 30 kpc). The frequency of quasars with FR II level extended radio emission is $\approx 2.3$ and $>0.4$ of quasars have FR I level extended radio emission. The lower limit simply reflects the flux density limit of the survey. The distribution of the long term time averaged jet powers of these quasars, $\bar{Q}$, has a broad peak $\sim 3\times 10^{44}$ ergs/sec that turns over below below $10^{44}$ ergs/sec and sources above $10^{45}$ ergs/sec are extremely rare. It is found that the correlation between the bolometric (total thermal) luminosity of the accretion flow, $L_{bol}$, and $\bar{Q}$ is not strong. The correlation of $\bar{Q}$ with narrow line luminosity is stronger than the correlation with broad line luminosity and the continuum luminosity. It is therefore concluded that previous interpretations of correlations of $\bar{Q}$ with narrow line strengths in radio galaxies as a direct correlation of jet power and accretion power have been overstated. It is explained why this interpretation mistakenly overlooks the sizeable fraction of sources with weak accretion luminosity and powerful jets discovered by Ogle et al (2006).Comment: To appear in ApJ Letter

Dynamic Boundaries of Event Horizon Magnetospheres

This Letter analyzes 3-dimensional simulations of Kerr black hole magnetospheres that obey the general relativistic equations of perfect magnetohydrodynamics (MHD). Particular emphasis is on the event horizon magnetosphere (EHM) which is defined as the the large scale poloidal magnetic flux that threads the event horizon of a black hole (This is distinct from the poloidal magnetic flux that threads the equatorial plane of the ergosphere, which forms the ergospheric disk magnetosphere). Standard MHD theoretical treatments of Poynting jets in the EHM are predicated on the assumption that the plasma comprising the boundaries of the EHM plays no role in producing the Poynting flux. The energy flux is electrodynamic in origin and it is essentially conserved from the horizon to infinity, this is known as the Blandford-Znajek (B-Z) mechanism. To the contrary, within the 3-D simulations, the lateral boundaries are strong pistons for MHD waves and actually inject prodigious quantities of Poynting flux into the EHM. At high black hole spin rates, strong sources of Poynting flux adjacent to the EHM from the ergospheric disk will actually diffuse to higher latitudes and swamp any putative B-Z effects. This is in contrast to lower spin rates, which are characterized by much lower output powers and modest amounts of Poynting flux are injected into the EHM from the accretion disk corona.Comment: To appear in MNRAS Letters. A high resolution version can be found at: http://85.20.11.14/hosting/punsly/MNRAS%20Letter7.20.07

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

© 2018 ESO. Reproduced with permission from Astronomy & Astrophysics. Content in the UH Research Archive is made available for personal research, educational, and non-commercial purposes only. Unless otherwise stated, all content is protected by copyright, and in the absence of an open license, permissions for further re-use should be sought from the publisher, the author, or other copyright holder.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 μ as from the central black hole. Furthermore, recent jet models indicate that a hollow "tubular" jet can explain a wide range of plausible broadband spectra originating from jetted plasma located within ~30 μ 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.Peer reviewe