1. Department of Physics, Stockholm University, AlbaNova, Stockholm, Sweden
2. Institute of condensed Matter and Nanosciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium
3. Theoretical Astrophysics, Department of Physics and Astronomy, Uppsala University, Box 516, S 75120, Uppsala, Sweden
4. Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, NM 87117, USA