1. Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, Florida 32901, USA
2. Center for Space Research, North-West University, Potchefstroom 2520, South Africa
3. State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China
4. Center for Space Plasma and Aeronomic Research and Department of Space Science, University of Alabama in Huntsville, Huntsville, Alabama 35899, USA