On the angular momentum transport due to vertical convection in accretion discs

TL;DR

This paper investigates whether turbulent thermal convection can effectively transport angular momentum in accretion discs, offering an alternative to magnetorotational instability, with results showing potential but weaker transport compared to heat transfer.

Contribution

It demonstrates through spectral methods that turbulent convection can drive outward angular momentum transport in accretion discs, highlighting a possible alternative mechanism.

Findings

Convection can produce outward angular momentum transport under certain conditions.

Transport due to convection is weaker than vertical heat transport.

Convection may influence disc evolution if a sufficiently unstable temperature profile exists.

Abstract

The mechanism of angular momentum transport in accretion discs has long been debated. Although the magnetorotational instability appears to be a promising process, poorly ionized regions of accretion discs may not undergo this instability. In this letter, we revisit the possibility of transporting angular momentum by turbulent thermal convection. Using high-resolution spectral methods, we show that strongly turbulent convection can drive outward angular momentum transport at a rate that is, under certain conditions, compatible with observations of discs. We find however that the angular momentum transport is always much weaker than the vertical heat transport. These results indicate that convection might be another way to explain global disc evolution, provided that a sufficiently unstable vertical temperature profile can be maintained.