Spiral-driven accretion in protoplanetary discs - I. 2D models

TL;DR

This study uses 2D simulations to show that inflow-induced shocks in non-magnetised protoplanetary discs generate spiral waves that effectively transport angular momentum, impacting disc evolution.

Contribution

It demonstrates the formation of long-lived spiral density waves and quantifies their role in angular momentum transport in non-magnetised protoplanetary discs.

Findings

Spiral density waves are generated by unstable accretion shocks.

These waves propagate inward over large distances.

Angular momentum transport rates are significant and cannot be ignored.

Abstract

We numerically investigate the dynamics of a 2D non-magnetised protoplanetary disc surrounded by an inflow coming from an external envelope. We find that the accretion shock between the disc and the inflow is unstable, leading to the generation of large-amplitude spiral density waves. These spiral waves propagate over long distances, down to radii at least ten times smaller than the accretion shock radius. We measure spiral-driven outward angular momentum transport with 1e-4 < alpha < 1e-2 for an inflow accretion rate Mout>1e-8 Msun/yr. We conclude that the interaction of the disc with its envelope leads to long-lived spiral density waves and radial angular momentum transport with rates that cannot be neglected in young non-magnetised protostellar discs.