Surprises in astrophysical gasdynamics

  title={Surprises in astrophysical gasdynamics},
  author={Steven A. Balbus and William J Potter},
  journal={Reports on Progress in Physics},
Much of astrophysics consists of the study of ionized gas under the influence of gravitational and magnetic fields. Thus, it is not possible to understand the astrophysical universe without a detailed knowledge of the dynamics of magnetized fluids. Fluid dynamics is, however, a notoriously tricky subject, in which it is all too easy for one’s a priori intuition to go astray. In this review, we seek to guide the reader through a series of illuminating yet deceptive problems, all with an… 


The assumption of a spatially uniform helium distribution in the intracluster medium (ICM) can lead to biases in the estimates of key cluster parameters if composition gradients are present. The

Dynamical Thermal Instability in Highly Supersonic Outflows

Acceleration can change the ionization of X-ray irradiated gas to the point that the gas becomes thermally unstable. Cloud formation, the expected outcome of thermal instability (TI), will be

The effect of rotation on the thermal instability of stratified galactic atmospheres – II. The formation of high-velocity clouds

Whether High Velocity Clouds (HVCs) can form by condensation of the hot ($T \sim 10^6 \, {\rm K}$) Galactic corona as a consequence of thermal instabilities has been controversial. Here we re-examine

Singular diffusionless limits of double-diffusive instabilities in magnetohydrodynamics

  • Oleg N. Kirillov
  • Mathematics, Physics
    Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
  • 2017
Stability analysis of amplitude transport equations of short-wavelength approximation finds that the threshold of the diffusionless AMRI via the Hamilton–Hopf bifurcation is a singular limit of the thresholds of the viscous and resistive AMRI corresponding to the dissipative Hopf b ifurcation and manifests itself as the Whitney umbrella singular point.

Exploring the physical properties of the cool circumgalactic medium with a semi-analytic model

We develop a semi-analytic model to explore the physical properties of cool pressure-confined circumgalactic clouds with mass ranging from $10$ to $10^{8} \, \rm M_{\odot}$ in a hot diffuse halo. We

Braginskii viscosity on an unstructured, moving mesh accelerated with super-time-stepping

We present a method for efficiently modelling Braginskii viscosity on an unstructured, moving mesh. Braginskii viscosity, i.e. anisotropic transport of momentum with respect to the direction of the

Short-wavelength local instabilities of a circular Couette flow with radial temperature gradient

We perform a linearized local stability analysis for short-wavelength perturbations of a circular Couette flow with a radial temperature gradient. Axisymmetric and non-axisymmetric perturbations are

The effect of rotation on the thermal instability of stratified galactic atmospheres – I. Local analysis

Observations show that (i) multiple gas phases can coexist in the atmospheres of galaxies and clusters; (ii) these atmospheres may be significantly rotating in the inner parts, with typical



Instability, turbulence, and enhanced transport in accretion disks

Recent years have witnessed dramatic progress in our understanding of how turbulence arises and transports angular momentum in astrophysical accretion disks. The key conceptual point has its origins

Theory of rotating stars

Ever since the first observations of sunspots in the early seventeenth century, stellar rotation has been a major topic in astronomy and astrophysics. Jean-Louis Tassoul synthesizes a large number of

Hydrodynamic turbulence cannot transport angular momentum effectively in astrophysical disks

A laboratory experiment is reported, demonstrating that non-magnetic quasi-keplerian flows at Reynolds numbers up to millions are essentially steady, indirectly support the magnetorotational instability as the likely cause of turbulence, even in cool disks.

Buoyancy Instabilities in a Weakly Collisional Intracluster Medium

The intracluster medium (ICM) of galaxy clusters is a weakly collisional plasma in which the transport of heat and momentum occurs primarily along magnetic-field lines. Anisotropic heat conduction

Dynamics of the Magnetoviscous Instability

In dilute astrophysical plasmas, the collisional mean free path of a particle can exceed its Larmor radius. Under these conditions, the thermal conductivity and viscosity of the plasma can be

Stability, Instability, and “Backward” Transport in Stratified Fluids

The stratification of entropy and the stratification of angular momentum are closely analogous. The analogy has been developed for a number of different problems in the fluid literature, but its

Buoyancy Instabilities in Weakly Magnetized Low-Collisionality Plasmas

I calculate the linear stability of a stratified low-collisionality plasma in the presence of a weak magnetic field. Heat is assumed to flow only along magnetic field lines. In the absence of a heat

The radiative zone of the Sun and the tachocline: stability of baroclinic patterns of differential rotation

Barotropic rotation and radiative equilibrium are mutually incompatible in stars. The issue is often addressed by allowing for a meridional circulation, but this is not devoid of theoretical

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We present equilibrium states of the interstellar gas, which has run down the perturbed magnetic field lines of a stratified, isothermal initial state under the action of a vertical galactic

Can conduction induce convection? On the non-linear saturation of buoyancy instabilities in dilute plasmas

We study the effects of anisotropic thermal conduction on low-collisionality, astrophysical plasmas using two- and three-dimensional magnetohydrodynamic simulations. Dilute, weakly magnetized plasmas