[1] Max Planck Inst Kernphys, D-69029 Heidelberg, Germany
[2] Yerevan Phys Inst, Yerevan 375036, Armenia
[3] UPS, CNRS, Ctr Etud Spatiale Rayonnements, F-31029 Toulouse 4, France
[4] Univ Hamburg, Inst Expt Phys, D-22761 Hamburg, Germany
[5] Humboldt Univ, Inst Phys, D-12489 Berlin, Germany
[6] Observ Paris, Sect Meudon, LUTH, CNRS,UMR 8102, F-92195 Meudon, France
[7] Univ Durham, Dept Phys, Durham DH1 3LE, England
[8] Ecole Polytech, Lab Leprince Ringuet, CNRS, IN2P3, F-91128 Palaiseau, France
[9] APC, F-75231 Paris 05, France
[10] Dublin Inst Adv Studies, Dublin 2, Ireland
[11] Landessternwarte Konigstuhl, D-69117 Heidelberg, Germany
[12] Univ Montpellier 2, Lab Phys Theor & Astroparticules, CNRS, IN2P3, F-34095 Montpellier 5, France
[13] Univ Grenoble 1, Lab Astrophys Grenoble, CNRS, INSU, F-38041 Grenoble 9, France
[14] Ctr Etud Saclay, CEA, DSM, DAPNIA, F-91191 Gif Sur Yvette, France
[15] North West Univ, Unit Space Phys, ZA-2520 Potchefstroom, South Africa
[16] Univ Paris 06, Lab Phys Nucl & Hautes Energies, CNRS, IN2P3, F-75252 Paris 5, France
[17] Univ Paris 07, Lab Phys Nucl & Hautes Energies, CNRS, IN2P3, F-75252 Paris 5, France
[18] Ruhr Univ Bochum, Inst Theoret Phys, Lehrstuhl Weltraum & Astrophys 4, D-44780 Bochum, Germany
[19] Charles Univ Prague, Inst Nucl & Particle Phys, CR-18000 Prague 8, Czech Republic
[20] Univ Namibia, Windhoek, Namibia