^a Institute for Cosmic Ray Research, University of Tokyo, Tokyo 188-8502, Japan

^b Faculty of Engineering, Yamanashi University, Kofu 400-8511, Japan

^c Faculty of Education, Yamanashi University, Kofu 400-8510, Japan

^d Department of Physics, Saitama University, Urawa 338-8570, Japan

^e Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan

^f Nishina Memorial Foundation, Komagome, Tokyo 113, Japan

^g Faculty of General Education, Hirosaki University, Hirosaki 036-8560, Japan

^h Department of Physics, Osaka City University, Osaka 558-8585, Japan

ⁱ Department of Physics, Kobe University, Kobe 657-8501, Japan

^j Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601, Japan

^k Nagoya University of Foreign Studies, Nissin, Aichi 470-0197, Japan

^l National Institute of Radiological Sciences, Chiba 263-8555, Japan

^m Department of Physics, Ehime University, Matsuyama 790-8577, Japan