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The magnetohydrodynamic simulation code FLOW (K. Lind, D. Payne, D. Meier, and R. Blandford 1989) has been used to simulate the Blandford-Payne mechanism for producing jets from magnetized accretion disks. The simulations were run on the Intel Delta massively parallel supercomputer at Caltech. At least one model has been found to produce a jet, and the parameters of that model lie within the region where magnetic outflows were predicted by Blandford and Payne. We will discuss additional models from a parameter study currently in progress and the viability of the Blandford-Payne model in light of the nonlinear MHD simulations.
A parameter study such as this would have been nearly impossible without the advent of massively-parallel supercomputers. Although FLOW was initially designed to be upgradable to such computers, nevertheless the modifications necessary for parallel operation involved changes or additions to a substantial fraction of the code (25\%). In light of this, we also will discuss the parallel algorithm, particularly the following features: decomposition of multi-dimensional MHD onto a massively parallel machine, methods for maintaining synchronization and approximate load balancing among the processors, and I/O. The implications of this project for parallelizing other codes will be discussed.
