[1] Max Planck Inst Kernphys, D-69117 Heidelberg, Germany
[2] Yerevan Phys Inst, Yerevan, Armenia
[3] Univ Durham, Dept Phys, Durham DH1 3HP, England
[4] UPS, CNRS, Ctr Etud Spatiale Rayonnements, Toulouse, France
[5] Univ Hamburg, Inst Expt Phys, Hamburg, Germany
[6] Univ Paris 07, APC, Observ Paris, CEA,CNRS,UMR 7164, Paris, France
[7] Humboldt Univ, Inst Phys, D-1086 Berlin, Germany
[8] Observ Paris, Sect Meudon, LUTH, CNRS,UMR 8102, Paris, France
[9] Univ Montpellier 2, Grp Astroparticules Montpellier, CNRS, IN2P3, F-34095 Montpellier, France
[10] Ecole Polytech, Lab Leprince Ringuet, CNRS, IN2P3, Palaiseau, France
[11] Dublin Inst Adv Studies, Dublin, Ireland
[12] Landessternwarte Konigstuhl, D-6900 Heidelberg, Germany
[13] Univ Grenoble 1, CNRS, INSU, Lab Astrophys Grenoble, F-38041 Grenoble, France
[14] CE Saclay, CEA, DSM, DAPNIA, Gif Sur Yvette, France
[15] North West Univ, Unit Space Phys, Potchefstroom, South Africa
[16] Univ Paris 06, Lab Phys Nucl & Hautes Energies, CNRS, IN2P3, F-75252 Paris, France
[17] Univ Paris 07, Lab Phys Nucl & Hautes Energies, CNRS, IN2P3, F-75221 Paris, France
[18] Ruhr Univ Bochum, Inst Theoret Phys, Lehrstuhl Weltraum & Astrophys 4, Bochum, Germany
[19] Charles Univ, Inst Nucl & Particle Phys, Prague, Czech Republic
[20] Univ Namibia, Windhoek, Namibia