Appearance of Jet-Driving Poynting Flux in Hot, Tenuous Accretion Disks Threaded by an Ordered Magnetic Field

TL;DR

This paper proposes a reformulation of the resistive RIAF model to include electric fields and effects of magnetic field changes, predicting jet launching from the inner disk region due to localized Poynting flux.

Contribution

It introduces a first-order correction to the resistive RIAF model, enabling the description of jet launching via electrodynamic processes in accretion disks.

Findings

Localized Poynting flux near the disk's inner edge suggests jet launching.

Rapid magnetic field changes occur in the same region.

Model predicts electrodynamic acceleration of jets from accretion disks.

Abstract

In a series of our previous works, a model of radiatively inefficient accretion flows (RIAFs) in a global magnetic field (so called resistive RIAF model) has proved its ability to account for many physical processes taking place in such accretion flows as realized in the nuclei of the galaxies believed to be accreting at a very small fraction of each Eddinton accretion rate. Within the present status of this model, however, the model cannot describe the launch of a self-confined bipolar jet from the vicinity of disk's inner edge, although it allows the existence of a thermal wind widely distributed over the disk surfaces. This is because the electric field (and hence the Poynting flux) vanishes everywhere in the disk, whereas such a jet in a globally ordered magnetic field is most likely to be accelerated electrodynamically. We show in the present paper that this defect can be overcome naturally if we reformulate the problem so as to admit a quasi-stationary change of the magnetic field (and hence the appearance of a non-irrotational electric field), and also restore all the terms of order epsilon ~ (v_r/v_{varphi})^2 < 1 (where v_r and v_{varphi} denote radial and azimuthal components, respectively, of the fluid velocity) which have been neglected altogether in the previous treatments. The restored effects are the inertial and magnetic draggings on the infalling matter. As an illustrative example, a model solution which is correct up to the first order in epsilon is derived under a set of plausible restrictions. The new solution predicts the appearance of a localized Poynting flux in a region near the disk inner edge, suggesting strongly that a jet is launched from this region. Another interesting prediction is the appearance of a rapid change of the magnetic field also localized to this region.