[1] St Petersburg State Univ, St Petersburg 198904, Russia
[2] Ctr Etud Spatiale Rayonnements, Toulouse, France
[3] Space Res Inst, Moscow, Russia
[4] Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA
[5] Univ Washington, Geophys Program, Seattle, WA 98195 USA
[6] Max Planck Inst Extraterr Phys, D-37075 Garching, Germany
[7] Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan
[8] Los Alamos Natl Lab, Los Alamos, NM USA