[1] Ctr Etud Spatiale Rayonnements, F-31029 Toulouse, France
[2] Max Planck Inst Extraterr Phys, D-85740 Garching, Germany
[3] CEA Saclay, SAP, F-91191 Gif Sur Yvette, France
[4] Univ Valencia, IFIC, E-46100 Burjassot, Spain
[5] Univ Catholique Louvain, Inst Phys Nucl, B-1348 Louvain, Belgium
[6] CNR, Ist Fis Cosm, I-20144 Milan, Italy
[7] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[8] Univ Calif San Diego, CASS 0111, La Jolla, CA 92093 USA
[9] Univ Calif Berkeley, SSL, Berkeley, CA 94720 USA
[10] Univ Birmingham, Space Res Grp, Birmingham B15 2TT, W Midlands, England