1. Department of Space Physics, School of Electronic Information; Wuhan University; Wuhan China
2. Helmholtz Centre Potsdam; GFZ German Research Centre for Geosciences; Potsdam Germany
3. Institute of Physics and Astronomy; University of Potsdam; Potsdam Germany
4. Department of Earth, Planetary, and Space Sciences; University of California; Los Angeles CA USA
5. Department of Mathematics and Statistics; Memorial University of Newfoundland; St. John's Newfoundland Canada