1. School of Science, Beijing Jiaotong University, Beijing 100044, China
2. Department of Modern Physics and School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026, China
3. Key Laboratory of Geospace Environment, CAS, Hefei, Anhui 230026, China
4. School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
5. Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
6. LSEC, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100190, China