•P. Homola¹, D. Gora¹, D. Heck², H. Klages ², J. Pekala¹, M. Risse², B. Wilczynska¹ und H. Wilczynski^1
1H.Niewodniczanksi Institute of Nuclear Physics, 31-342 Krakow, Poland
²Forschungszentrum Karlsruhe, Institut für Kernphysik, Postfach 3640, 76021 Karlsruhe

The origin of cosmic rays at the highest energies is still unclear. In some so-called top-down scenarios, a considerable fraction of particles at energies exceeding 10 EeV are predicted to be photons. Photons at such high energies can interact with the Earth's magnetic field, forming an electron-positron pair, which in turn emits synchrotron radiation. In this way, instead of a single high-energetic particle, a bunch of particles enters as a preshower the atmosphere, which influences the characteristics of the air shower formed. In the simulation code CORSIKA, this preshowering has been included. The preshower physics is reviewed and results of the complete CORSIKA simulations are presented. Implications for the detection of air showers initiated by high-energy photons are discussed.