1. Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
2. CAS Key Laboratory of Geospace Environment, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
3. College of Science, China University of Mining and Technology, Xuzhou, Jiangsu 221116, People's Republic of China