Relativistic jet acceleration region in a black hole magnetosphere

TL;DR

This paper analyzes the acceleration regions of relativistic jets in black hole magnetospheres, focusing on energy conversion and flow parameters, with implications for understanding the M87 jet via the Blandford-Znajek process.

Contribution

It applies trans-magnetosonic flow solutions to model jet acceleration and estimates key flow surfaces and energy extraction parameters relevant to the M87 jet.

Findings

Identification of flow surface locations such as the Alfvén surface.

Parameter dependence analysis of jet acceleration efficiency.

Confirmation of electromagnetic energy extraction via the Blandford-Znajek process.

Abstract

We discuss stationary and axisymmetric trans-magnetosonic outflows in the magnetosphere of a rotating black hole (BH). Ejected plasma from the plasma source located near the BH is accelerated far away to form a relativistic jet. In this study, the plasma acceleration efficiency and conversion of fluid energy from electromagnetic energy are considered by employing the trans-fast magnetosonic flow solution derived by Takahashi & Tomimatsu (2008). Considering the parameter dependence of magnetohydrodynamical flows, we search for the parameters of the trans-magnetosonic outflow solution to the recent M87 jet observations and obtain the angular velocity values of the magnetic field line and angular momentum of the outflow in the magnetized jet flow. Therefore, we estimate the locations of the outer light surface, Alfv\'en surface, and separation surface of the flow. We also discuss the electromagnetic energy flux from the rotating BH (i.e., the Blandford-Znajek process), which suggests that the energy extraction mechanism is effective for the M87 relativistic jet.