Enhanced MHD transport in astrophysical accretion flows: turbulence, winds and jets

TL;DR

This paper introduces a new theoretical model and ongoing 3D simulations to better understand how MHD turbulence, winds, and jets influence accretion processes and energy transport in astrophysical systems, especially around black holes.

Contribution

It proposes a novel model for enhanced vertical momentum and energy transport in accretion disks via MHD winds and turbulence, supported by new global 3D simulation efforts.

Findings

Enhanced vertical transport by MHD winds and turbulence in accretion disks.

Potential explanation for the formation of large-scale magnetic fields and jets.

Insights into the evolution of turbulent magnetic fields into ordered structures.

Abstract

Astrophysical accretion is arguably the most prevalent physical process in the Universe; it occurs during the birth and death of individual stars and plays a pivotal role in the evolution of entire galaxies. Accretion onto a black hole, in particular, is also the most efficient mechanism known in nature, converting up to 40% of accreting rest mass energy into spectacular forms such as high-energy (X-ray and gamma-ray) emission and relativistic jets. Whilst magnetic fields are thought to be ultimately responsible for these phenomena, our understanding of the microphysics of MHD turbulence in accretion flows as well as large-scale MHD outflows remains far from complete. We present a new theoretical model for astrophysical disk accretion which considers enhanced vertical transport of momentum and energy by MHD winds and jets, as well as transport resulting from MHD turbulence. We also describe new global, 3D simulations that we are currently developing to investigate the extent to which non-ideal MHD effects may explain how small-scale, turbulent fields (generated by the magnetorotational instability -- MRI) might evolve into large-scale, ordered fields that produce a magnetized corona and/or jets where the highest energy phenomena necessarily originate.