John F. Hawley, Professor

Professional Data:

Teaching:

In the spring semester I teach Introduction to Cosmology. The home pages for these courses provide a brief preview of their content.

The cosmology course uses my textbook Foundations of Modern Cosmology which is published by Oxford University Press.

Research interests:

Computational Astrophysics

My research activities have primarily been concerned with accretion disks and related phenomena. I have chosen to focus on the basic physics of such systems through the use of computational finite-difference techniques. This approach necessitates the development of numerical algorithms, and the devotion of considerable effort to programming, computation, and visualization. Pictured here is an an image from a three dimensional simulation of a magnetized accretion torus.

Some past papers on numerical algorithms include

Accretion Disks

A good deal of my current research is concerned with the behavior of gas in orbit around compact stars and black holes, particularly on the stability properties of accretion disks. For example, recent simulations have investigated the generation of magnetohydrodynamical turbulence in disks and the resulting angular momentum transport. This turbulence arises from the presence of a weak magnetic field instability in accretion disks. The paper that describes the magnetorotational instability is

Disk review papers include:


Disk Simulations on the Web

Here are recent papers on global accretion disk simulations:

The Dynamical Structure of Nonradiative Accretion Flows Astrophysical Journal, 573, 749 (2002). The web version of this paper provides MPEG animations.

High Resolution Simulations of the Plunging Region in a Pseudo-Newtonian Potential: Dependence on Numerical Resolution and Field Topology Astrophysical Journal, 566, 164 (2002). The web version of this paper also provides MPEG animations.

A Magnetohydrodynamic Nonradiative Accretion Flow in Three Dimensions Astrophysical Journal Letters, 554, (2001) The preprint is on the web along with a MPEG animations, and a color version of figure 1.

Global MHD Simulations of Cylindrical Keplerian Disks. Astrophysical Journal, 554, 534 (2001). The preprint is on the web along with MPEG animations of the simulations.

Global MHD Simulation of the Inner Accretion Disk in a Pseudo-Newtonian Potential. Astrophysical Journal, 548, 348 (2001). The web version of this paper includes MPEG animations of the simulation.

Global Magnetohydrodynamical Simulations of Accretion Tori Astrophysical Journal, 528, 462 (2000). The web version of this paper also provides MPEG animations.

Other Disk Simulations

This image shows a cross section through a magnetized disk in which the magnetorotational instability has created turbulence. The blue indicates gas with less than Keplerian angular momentum; the red is gas with excess angular momentum. The MHD instability is very effective at creating the angular momentum transport required to make accretion disks accrete. This is from the two dimensional simulations described in


 

This image shows the density distribution from a three-dimensional MHD simulation of a small portion of a stratified accretion disk. This disk is threaded with an weak toroidal magnetic field. A 2 MB MPEG movie shows the development and evolution of angular momentum perturbations in this disk. More about simulations of this type can be found in


 

Papers on the local hydrodynamic stability of differential rotation:

Local MHD shearing box simulations:

Global Three Dimensional accretion disk simulations: