Jets, disc-winds and oscillations in general relativistic, magnetically driven flows around black hole

TL;DR

This study uses axisymmetric GRMHD simulations to explore how magnetic field strength and structure influence jet and disc wind launching around black holes, revealing mechanisms behind observed oscillations and flaring activities.

Contribution

It provides new insights into the magnetic mechanisms driving relativistic jets and disc winds, and links these processes to spectral state transitions in black hole X-ray binaries.

Findings

Jets are driven by the Blandford-Znajek mechanism.

Disc winds are driven by the Blandford-Payne mechanism.

Plasmoid formation and disc oscillations are linked to magnetic reconnection.

Abstract

Relativistic jets and disc-winds are typically observed in BH-XRBs and AGNs. However, many physical details of jet launching and the driving of disc winds from the underlying accretion disc are still not fully understood. In this study, we further investigate the role of the magnetic field strength and structure in launching jets and disc winds. In particular, we explore the connection between jet, wind, and the accretion disc around the central black hole. We perform axisymmetric GRMHD simulations of the accretion-ejection system using adaptive mesh refinement. Essentially, our simulations are initiated with a thin accretion disc in equilibrium. An extensive parametric study by choosing different combinations of magnetic field strength and initial magnetic field inclination is also performed. Our study finds relativistic jets driven by the Blandford \& Znajek (BZ) mechanism and the disc-wind driven by the Blandford \& Payne (BP) mechanism. We also find that plasmoids are formed due to the reconnection events, and these plasmoids advect with disc-winds. As a result, the tension force due to the poloidal magnetic field is enhanced in the inner part of the accretion disc, resulting in disc truncation and oscillation. These oscillations result in flaring activities in the jet mass flow rates. We find simulation runs with a lower value of the plasma-$\beta$, and lower inclination angle parameters are more prone to the formation of plasmoids and subsequent inner disc oscillations. Our models provide a possible template to understand spectral state transition phenomena in BH-XRBs.