[1] Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA
[2] Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA
[3] Univ Appl Sci & Arts Northwestern Switzerland, Sch Engn, Inst Technol 4D, CH-5210 Windisch, Switzerland
[4] Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA
[5] Kyung Hee Univ, Sch Space Res, Seoul, South Korea