1. Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, USA.
2. Institutes of Astronomy and Space Science, National Central University, Chung Li 32054, Taiwan.
3. Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, USA.
4. Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA.
5. NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.