Blob formation and ejection from the radiative inefficient accretion flow around massive black hole

TL;DR

This study uses 2D MHD simulations to explore magnetic reconnection near a black hole, revealing blob formation and ejection mechanisms consistent with episodic jet models.

Contribution

It demonstrates how magnetic reconnection can produce blobs and jets near black holes, with detailed simulation of energy conversion and vortex structures.

Findings

Blob ejection driven by magnetic reconnection near black hole

Higher energy conversion efficiency closer to the black hole

Vortex structures in blobs due to Kelvin-Helmholtz instability

Abstract

We study the small scale magnetic reconnection above the radiative inefficient accretion flow around massive black hole via 2D magnetohydrodynamics (MHD) numerical simulation, in order to model the blob formation and ejection from the accretion flow around Sgr A*. The connection of both the newly emerging magnetic field and the pre-existing magnetic field is investigated to check whether blobs could be driven in the environment of black hole accretion disc. After the magnetic connection, both the velocity and temperature of the plasma can be comparable to the inferred physical properties at the base of the observed blob ejection. For illustration, three small boxes which are located within 40 Schwarzschild radii from the central black hole are chosen as our simulation areas. At the beginning of the reconnections, the fluid is pulled toward the central black hole due to the gravitational attraction and the current sheet produced by the reconnection is also pulled toward the same direction, consequently, the resulting outflows move both upwards and towards the symmetry axis of the central black hole. Eventually, huge blobs appear, which supports the catastrophe model of episodic jets \citep{2009MNRAS.395.2183Y}. It is also found that the closer to the black hole the magnetic connection happens, the higher the converting efficiency of the magnetic energy into the heat and kinetic energy. For these inner blobs, they have vortex structure due to the K-H instability, which happens along the current sheet separating the fluids with different speed.