1. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
2. Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
3. Oden Institute for Computational Engineering and Sciences, University of Texas, Austin, Texas 78712, USA
4. Department of Mathematics and Statistics, University of Colorado, Denver, Colorado 80204, USA
5. Center for Applied Scientific Computing, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
6. Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
7. Space Science Center and Department of Physics, University of New Hampshire, Durham, New Hampshire 03824, USA
8. Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany