1. National Institute of Polar Research; Tachikawa Japan
2. Planetary Plasma and Atmospheric Research Center; Graduate School of Science; Tohoku University; Sendai Japan
3. Solar-Terrestrial Environment Laboratory; Nagoya University; Nagoya Japan
4. Geophysical Institute; University of Alaska; Fairbanks Alaska USA
5. Department of Geophysics; Graduate School of Science; Tohoku University; Sendai Japan
6. Institute for Astronomy; University of Hawaii; Pukalani Hawaii USA