1. T-5 Applied Mathematics and Plasma Physics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2. Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
3. Asher Space Research Institute, Technion (Israel Institute of Technology), Haifa, Israel
4. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA