1. Department of Atmospheric and Oceanic Sciences; University of California; Los Angeles California USA
2. Solar-Terrestrial Environment Laboratory; Nagoya University; Nagoya Japan
3. Institute of Geophysics and Planetary Physics, Department of Earth and Space Sciences; University of California; Los Angeles California USA
4. Space Sciences Laboratory; University of California; Berkeley California USA
5. Laboratoire de Physique des Plasmas, Ecole Polytechnique; Université Pierre et Marie Curie, Paris 6, CNRS; Vélizy France
6. Institut für Geophysik und extraterrestrische Physik; Technischen Universität Braunschweig; Braunschweig Germany