Production mechanisms of multiple primaries for Cosmic Rays Showers
  We investigate the physical mechanism of the GZ-effect that could explain the production of multiple primaries from an event initiated outside the Earth's atmosphere. In this case, there would correspondingly be multiple extensive air showers in temporal coincidence at ground, even for detectors separated by many kilometers, and also showers initiated by primaries of different energies could consequently have a common source. We analyse the perspectives and limits of some models and discuss the experimental counterparts. 
Giovanni Imponente and Gabriella Sartorelli