1. Computational Simulations of Relativistic Jets using the Cubed Sphere Grid Previous Grid Constructions The objective of our study is to determine what establishes the jet orientation in black hole accretion disk systems. Unfortunately, fundamental parameters like angular momentum are not directly observable, and analytic models are difficult to develop. For these reasons, we use numerical models to study these systems. Current grid constructions are inadequate for simultaneously simulating disks and jets. In order to do so, we must develop a new grid system. Christopher C. Lindner, P. Chris Fragile Abstract Relativistic Jets are streams of plasma moving throughout the universe at speeds up to 99% the speed of light. They produce high- energy X-ray, radio, and visible radiation that are observable from great distances across the universe. Many of these jets have been attributed to black hole accretion disk systems. In these systems, a disk of material surrounds a black hole, and through magnetic processes the material accretes onto the black hole. Relativistic jets originating from the Crab Nebula (above) and the galaxy M87 (below) Accretion disk simulations can be run in two or three dimensions. In two dimensional simulations, we consider a “slice” of the disk, and can treat it as an azimuthal average of the entire disk. However, in studies of systems where the angular momentum of the disk is not aligned with the angular momentum of the black hole, our symmetry is broken, and we must study our problem in three dimensions. The cubed sphere grid structure is essentially 6 cubes that together are morphed in a sphere. The resulting domain features no poles and has an even distribution of zones in each of the six domains. Our code is designed to dedicate each block to one processor. If more processors are used, each block can be radially subdivided. For simulations where the polar region is not being studied, we can restrict our simulation to 1, 2, or 4 blocks to limit the computational expense. The Cubed Sphere Traditionally we have used the spherical polar coordinate grid for studying this type of problem. Though this is sufficient for studying the disk itself, the spherical polar mesh is flawed in that it features two poles which create numerical irregularities in these regions. This makes it virtually impossible to conclusively study flows near the poles, including jets. If we wish to study jets in these systems, we must implement a new coordinate system that both adequately conserves angular momentum and is well defined along the poles. Current and future work on the Cubed Sphere Thus far we have run several test problems to determine the effectiveness of the cubed sphere grid including rotating fluids around the grid, relativistic jet simulations, and black hole torus accretion simulations. In the future we plan to run full, high- resolution simulations of the black hole accretion disk problem and develop analysis tools to allow us to further study relativistic jet production and orientation in black hole accretion disk systems. Simulations run on the cubed sphere grid: a pulse of liquid circles the grid (left), an adaptation of the Sedov Blast Wave to simulate relativistic jets (center), and an accretion disk falling into a black hole (right) We gratefully acknowledge the support of Faculty R&D and SURF grants from the College of Charleston and a REAP Grant from the South Carolina Space Grant Consortium. Acknowledgements