Parametric instability in a free evolving warped protoplanetary disc

TL;DR

This paper demonstrates the first global simulation of parametric instability in warped protoplanetary discs at high resolution, revealing turbulence that damps warps rapidly, with implications for disc evolution.

Contribution

It introduces a hybrid Godunov-type Lagrangian method for high-resolution global simulations, capturing turbulence and warp damping due to parametric instability.

Findings

Turbulence damps warp within one bending-wave crossing time.

Global simulations confirm linear bending-wave propagation before instability.

Warp damping affects disc evolution and warp maintenance mechanisms.

Abstract

Warped accretion discs of low viscosity are prone to hydrodynamic instability due to parametric resonance of inertial waves as confirmed by local simulations. Global simulations of warped discs, using either smoothed particle hydrodynamics (SPH) or grid-based codes, are ubiquitous but no such instability has been seen. Here we utilize a hybrid Godunov-type Lagrangian method to study parametric instability in global simulations of warped Keplerian discs at unprecedentedly high resolution (up to 120 million particles). In the global simulations, the propagation of the warp is well described by the linear bending-wave equations before the instability sets in. The ensuing turbulence, captured for the first time in a global simulation, damps relative orbital inclinations and leads to a decrease in the angular momentum deficit. As a result, the warp undergoes significant damping within one bending-wave crossing time. Observed protoplanetary disc warps are likely maintained by companions or aftermath of disc breaking.