Energy dissipation and angular momentum transfer within a magnetically torqued accretion disc

TL;DR

This paper analyzes how magnetic connections and the Blandford-Payne process facilitate energy and angular momentum transfer in accretion discs, deriving criteria for viscous torque and outflow efficiency to maintain equilibrium.

Contribution

It introduces a new criterion for viscous torque and quantifies the conditions under which magnetic and outflow processes regulate angular momentum in accretion discs.

Findings

The Blandford-Payne process must exceed a critical efficiency to effectively remove angular momentum.

Magnetic connection influences the redistribution of energy and angular momentum within and beyond the disc.

A derived criterion ensures the overall angular momentum equilibrium in accretion disc systems.

Abstract

We discuss transportation and redistribution of energy and angular momentum in the magnetic connection (MC) process and Blandford-Payne (BP) process. The MC results in readjusting the interior viscous torque, and its effects are operative not only in but also beyond the MC region. The BP process is invoked to transfer the "excessive" angular momentum from an accretion disc. In addition, we derive a criterion for the interior viscous torque to resolve the puzzle of the overall equilibrium of angular momentum in disc accretion. It turns out that the BP efficiency of extracting angular momentum and the intensity of the outflow are required to be greater than some critical values.