Laboratory Studies of Magnetorotational Instabilities in a Galium Disk

Princeton University, Princeton NJ

Investigators

Abstract

AST 0205903 Goodman Quasars and X-ray binary stars are examples of astronomical objects that shine by converting the gravitational energy of gas orbiting a black hole into heat and radiation. The gas arranges itself into a flat disk centered on the black hole. Similar disks surround young stars and form planets. Astrophysicists postulate that turbulent friction between neighboring rings of these disks turns this orbital motion into heat. Most believe that this turbulence arises from a magnetic instability that has not yet been reproduced on earth except in computer simulations. The instability requires a gas or liquid of high electrical conductivity, a condition usually satisfied in space and in stars but not on earth. Air, water, and other common fluids are poor conductors of electricity while ionized plasmas created for fusion research are good conductors but too rigidly magnetized. This project will study astrophysical instability and turbulence in a small laboratory experiment using an alloy of gallium, a metal that is liquid at room temperature, less viscous than water, more conducting than mercury, and safer to handle. This will be set into rapid rotation between concentric cylinders in a strong magnetic field---a system dynamically similar to an astrophysical disk. The goals are to confirm previous computer predictions of the instability, to study its dependence on rotation, shear, and field strength, to validate computer simulations, and perhaps to demonstrate incipient turbulence. The results may confirm our understanding of astrophysical disk turbulence, which cannot yet be observed directly. ***