[1] Ehime Univ, Dept Phys, Matsuyama, Ehime 7908577, Japan
[2] Osaka Univ, Dept Earth & Space Sci, Osaka 5600043, Japan
[3] Hiroshima Univ, Dept Phys Sci, Hiroshima 7398526, Japan
[4] Univ St Andrews, Sch Phys & Astron, SUPA, St Andrews KY16 9SS, Fife, Scotland
[5] RIKEN, Wako, Saitama 3510198, Japan
[6] Univ Tokyo, Dept Phys, Bunkyo Ku, Tokyo 1130033, Japan
[7] Nagoya Univ, Dept Phys, Chikusa Ku, Nagoya, Aichi 4648602, Japan
[8] NASA, Goddard Space Flight Ctr, Astrophys Sci Div, Greenbelt, MD 20771 USA
[9] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA
[10] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England
[11] Univ Keele, Sch Phys & Geog Sci, Astrophys Grp, Keele ST5 5BG, Staffs, England
[12] Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan