GYRO Code Cracks Gyrokinetic-Maxwell Equations to Predict Microturbulence in Plasmas
To model turbulence inside a fusion reactor, theoretical physicist Dr. Ron Waltz and computational scientist Dr. Jeff Candy of General Atomics (figure 9), collaborators since 1999, wrote a global gyrokinetic software code called GYRO starting from the GS2 "flux-tube" gyrokinetic developed by Dr. Mike Kotschenreuther (University of Texas-Austin) and Dr. Bill Dorland (University of Maryland). Using the Cray X1E Phoenix supercomputer at the NCCS, Dr. Waltz and Dr. Candy recently ran the code on most of the Phoenix supercomputer processors for a week, using nearly all of the machine's associated memory to follow the motion of 674 million coordinate or "phase space" points in time--far more than the 100 Dr. Waltz started with in 1981.
"GYRO was the first gyrokinetic code with enough physics to simulate the transport in existing tokamaks--nonlinear, electromagnetic, global," Dr. Candy says. "Attempts to combine these three physics elements [with existing methods] had failed for approximately a decade. GYRO, which uses fixed-grid (Eulerian) algorithms, was able to overcome the difficulties which plagued earlier attempts."
Figure 9. Dr. Candy (left) and Dr. Waltz (right) wrote General Atomics' GYRO code to model turbulence inside a fusion reactor. For a decade, earlier codes had failed to combine nonlinear, electromagnetic, and global physics elements. GYRO used fixed-grid algorithms and provided the first convincing reproduction of experimental data using first-principles simulations.
Dr. Waltz and Dr. Candy designed the code to run on nearly all modern computing platforms, from laptops to supercomputer systems such as the CRAY X1E, XT3, and XT4 and IBM Blue Gene. Developed at General Atomics, GYRO solves the gyrokinetic-Maxwell equations, which describe the interaction between the turbulently fluctuating electromagnetic fields and the distribution functions of the ions and electrons. It tracks the transport of all plasma particles--mainly deuterium (and tritium) ions and electrons--as well as the transport of their heat energy. It pinpoints particle locations and drift velocities.
The code allowed the team to model gyrokinetic microturbulence, or instabilities in the plasma. They were able to study in electromagnetic detail what happens to plasma locally and globally throughout the tokamak in a full or partial torus. (It turns out simulating part of the doughnut gives almost as much information as simulating the entire structure, but at a much lower cost.) They were able to simulate plasmas of different shapes and sizes and demonstrate how shear in the E × B velocity from the background radial electric field can greatly reduce the transport, an important effect little studied by other gyrokinetic codes.
Freely available for anyone to use, the open-source software code has been employed by researchers at other institutions, including the Commissariat ŕ l'Énergie Atomique in Cadarache, France; University of Texas; Princeton Plasma Physics Laboratory; Oak Ridge National Laboratory; and Max-Planck-Institut für Plasmaphysik in Germany, as well as graduate students and postdoctoral fellows at the University of California-San Diego, University of California-Los Angeles, and University of Wisconsin.
The use of gyrokinetic codes has expanded from nuclear fusion to astrophysics. A University of California-Berkeley-led group of university researchers has even used the gyrokinetic code GS2 to model plasma heating in nebulas.
Further Reading

More about GYRO can be found at:
http://fusion.gat.com/theory/gyro

To view a brief GYRO-enabled animation of turbulent energy transport inside a tokamak, visit: http://fusion.gat.com/THEORY/images/0/0f/N32o6d0.8.mpg