1. Department of Atmospheric and Oceanic Sciences; UCLA; Los Angeles California USA
2. Department of Physics and Astronomy; University of Calgary; Calgary Alberta Canada
3. Institute of Geophysics and Planetary Physics/Earth and Space Sciences; UCLA; Los Angeles California USA
4. Space Sciences Laboratory; University of California; Berkeley California USA
5. Laboratoire de Physique des Plasmas; Ecole Polytechnique; Palaiseau France