author={Orkan M. Umurhan and Karim Shariff and Jeffrey N. Cuzzi},
  journal={The Astrophysical Journal},
A linear analysis of the zombie vortex instability (ZVI) is performed in a stratified shearing sheet setting for three model barotropic shear flows. The linear analysis is done by utilizing a Green’s function formulation to resolve the critical layers of the associated normal-mode problem. The instability is the result of a resonant interaction between a Rossby wave and a gravity wave that we refer to as Z-modes. The associated critical layer is the location where the Doppler-shifted frequency… 

Baroclinic critical layers in rotating stratified shear flows

In this thesis, we study baroclinic critical layers in rotating stratified shear flows. Baroclinic critical layers are characterized by strong amplitudes surrounding the singular points of the steady

Zombie Vortex Instability. III. Persistence with Nonuniform Stratification and Radiative Damping

The Zombie Vortex Instability (ZVI) occurs in the dead zones of protoplanetary disks (PPDs), where perturbations excite baroclinic critical layers, generating “zombie” vortices and turbulence. In

Global Simulations of the Vertical Shear Instability with Nonideal Magnetohydrodynamic Effects

The mechanisms of angular momentum transport and the level of turbulence in protoplanetary disks (PPDs) are crucial for understanding many aspects of planet formation. In recent years, it has been

Zombie vortex instability in the protoplanetary disk: can we find it in the lab?

Without instabilities, the gas in the protoplanetary disk approximately a forming protostar remains in orbit rather than falling onto the protostar and completing its formation into a star. Moreover

On the vertical shear instability in magnetized protoplanetary discs

The vertical shear instability (VSI) is a robust phenomenon in irradiated protoplanetary disks (PPDs). While there is extensive literature on the VSI in the hydrodynamic limit, PPDs are expected to

Efficiency of thermal relaxation by radiative processes in protoplanetary discs: constraints on hydrodynamic turbulence

Hydrodynamic, non-magnetic instabilities can provide turbulent stress in the regions of protoplanetary discs, where the MRI can not develop. The induced motions influence the grain growth, from which

Gas and Dust Dynamics in Starlight-heated Protoplanetary Disks

Theoretical models of the ionization state in protoplanetary disks suggest the existence of large areas with low ionization and weak coupling between the gas and magnetic fields. In this regime

The Initial Conditions for Planet Formation: Turbulence Driven by Hydrodynamical Instabilities in Disks around Young Stars

  • W. LyraO. Umurhan
  • Physics, Geology
    Publications of the Astronomical Society of the Pacific
  • 2019
This review examines recent theoretical developments in our understanding of turbulence in cold, non-magnetically active, planetesimal-forming regions of protoplanetary disks that we refer to

Mapping the Conditions for Hydrodynamic Instability on Steady-State Accretion Models of Protoplanetary Disks

Hydrodynamic instabilities in disks around young stars depend on the thermodynamic stratification of the disk and on the local rate of thermal relaxation. Here, we map the spatial extent of unstable

Radiation Hydrodynamical Turbulence in Protoplanetary Disks: Numerical Models and Observational Constraints

Planets are born in protostellar disks, which are now observed with enough resolution to address questions about internal gas flows. Magnetic forces are possibly drivers of the flows, but ionization



Zombie Vortex Instability I: A Purely Hydrodynamic Instability to Resurrect the Dead Zones of Protoplanetary Disks

There is considerable interest in hydrodynamic instabilities in dead zones of protoplanetary disks as a mechanism for driving angular momentum transport and as a source of particle-trapping vortices

A hydrodynamic shear instability in stratified disks

We discuss the possibility that astrophysical accretion disks are dynamically unstable to non-axisymmetric distur- bances with characteristic scales much smaller than the vertical scale height. The

Potential vorticity dynamics in the framework of disk shallow-water theory - I. The Rossby wave instability

Context. The Rossby wave instability in astrophysical disks is a potentially important mechanism for driving angular momentum transport in disks. Aims. We attempt to more clearly understand this

The onset of meandering in a barotropic jet

This study explores the dynamics of an unstable jet of two-dimensional, incompressible fluid on the beta-plane. In the inviscid limit, standard weakly nonlinear theory fails to give a low-order

On the mechanism of shear flow instabilities

In homogeneous and density-stratified inviscid shear flows, the mechanism for instability that is most commonly invoked and discussed is Kelvin–Helmholtz instability, as it occurs for a simple

Rossby Wave Instability of Thin Accretion Disks. II. Detailed Linear Theory

In an earlier work we identified a global, nonaxisymmetric instability associated with the presence of an extreme in the radial profile of the key function ℒ(r) ≡ (ΣΩ/κ2)S2/Γ in a thin, inviscid,

Rossby Wave Instability of Thin Accretion Disks. III. Nonlinear Simulations

We study the nonlinear evolution of the Rossby wave instability in thin disks using global two-dimensional hydrodynamic simulations. The detailed linear theory of this nonaxisymmetric instability was

The subcritical baroclinic instability in local accretion disc models

(abridged) Aims: We present new results exhibiting a subcritical baroclinic instability (SBI) in local shearing box models. We describe the 2D and 3D behaviour of this instability using numerical

Rossby Wave Instability of Keplerian Accretion Disks

We find a linear instability of nonaxisymmetric Rossby waves in a thin nonmagnetized Keplerian disk when there is a local maximum in the radial profile of a key function ℒ(r)≡ℱ(r)S2/Γ(r), where

The baroclinic instability in the context of layered accretion - Self-sustained vortices and their magnetic stability in local compressible unstratified models of protoplanetary disks

Context. Turbulence and angular momentum transport in accretion disks remains a topic of debate. With the realization that dead zones are robust features of protoplanetary disks, the search for