1. School of Space and Environment; Beihang University; Beijing China
2. Swedish Institute of Space Physics; Uppsala Sweden
3. Center for Mathematical Plasma Astrophysics; KU Leuven; Leuven Belgium
4. The Blackett Laboratory; Imperial College London; London UK
5. Laboratoire de Physique des Plasmas; CNRS/Ecole Polytechnique/UPMC; Palaiseau France