The initial conditions for planet formation: Turbulence driven by hydrodynamical instabilities in disks around young stars

TL;DR

This review explores recent theoretical advances in understanding turbulence driven by hydrodynamical instabilities in the non-magnetized, planet-forming regions of protoplanetary disks, focusing on three key instability mechanisms.

Contribution

It provides a comprehensive overview of the hydrodynamical instabilities that can generate turbulence in Ohmic zones of protoplanetary disks, highlighting recent developments and their conditions of activity.

Findings

Identifies three main turbulence mechanisms: Vertical Shear Instability, Convective Overstability, Zombie Vortex Instability.

Summarizes the properties and limitations of each instability.

Discusses the conditions under which these instabilities are active in protoplanetary disks.

Abstract

This review examines recent theoretical developments in our understanding of turbulence in cold, non-magnetically active, planetesimal forming regions of protoplanetary disks which we refer to throughout as "Ohmic zones". We give a brief background introduction to the subject of disk turbulence followed by a terse pedagogical review of the phenomenology of hydrodynamic turbulence. The equations governing the dynamics of cold astrophysical disks are given and basic flow states are described. We discuss the Solberg-Hoiland conditions required for stability, and the three recently identified turbulence generating mechanisms possibly active in protoplanetary disk Ohmic zones, namely, (i) the Vertical Shear Instability, (ii) The Convective Overstability and (iii) the Zombie Vortex Instability. We summarize the properties of these processes, identify their limitations and discuss where and under what conditions these processes are active in protoplanetary disk Ohmic zones.