1. Center for Mathematical Plasma Astrophysics, Department of Mathematics, KULeuven (University of Leuven), Celestijnenlaan 200B, B-3001 Leuven, Belgium
2. Swedish Institute of Space Physics, Uppsala, Sweden
3. Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
4. Center for Integrated Plasma Studies, University of Colorado Boulder, Gamow Tower, Boulder, 80309-0390 Colorado, USA
5. Department of Computational Science and Technologies, KTH Royal Institute of Technology, Stockholm, Sweden