Accretion disks play a prominent role in modern astrophysics, yet we remain largely ignorant of their detailed structure and local dynamics. The importance of angular momentum transport has been understood for a long time, but for many years our understanding of disks has been built on a parameterization of some unknown transport mechanism. In addition to local sources of transport such as MHD turbulence, global processes may also contribute to the transport of angular momentum in accretion disks. In particular, spiral shock waves can act as a local sink for angular momentum. Because these waves are traveling slower than the local Keplerian velocity, they contain negative angular momentum, and any dissipation at the shock will decrease the angular momentum of the orbiting gas. While spiral waves can be produced by a variety of sources, they arise naturally in binary star systems such as X-ray binaries, cataclysmic variables, and binary proto-stars, where the gravitational pull of a binary companion creates a two-armed spiral shock wave that co-rotates with the binary system.

There has been a great deal of numerical work regarding spiral waves in accretion disks. The results of these simulations suggest that spiral waves are a robust feature of accretion disks in binary systems, and that these spiral shocks can indeed transport mass and angular momentum through the disk. They do not, however, provide a quantitative measure of this transport. The goal of this work is to measure an effective alpha due to spiral shocks excited in accretion disks by the tidal forces of a binary companion.