[1] Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2AZ, England
[2] CESR, F-31028 Toulouse, France
[3] CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA
[4] Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England
[5] KFKI Res Inst Particle & Nucl Phys, H-1525 Budapest, Hungary
[6] Tech Univ Carolo Wilhelmina Braunschweig, D-38106 Braunschweig, Germany
[7] Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA
[8] Univ Cologne, Inst Geophys & Meteorol, D-50923 Cologne, Germany
[9] European Space Agcy, F-75738 Paris, France