A COMPLETE SIMULATION OF COSMIC RAYS ACCESS TO A SPACE STATION

The Cosmic Rays (hereafter CR) flux we can measure near the Earth is the result of a complex trajectory inside the geomagnetic field. On one side this acts like a shield for low energy primary CR, on the other side middle and high energy CR are focused and driven into preferential directions to reach the Earth. Excluding any kind of energy loss we can say that the energy spectrum in the solar cavity is essentially the same we measure at the Earth, but the magnetic field effect is to transform a (mostly) isotropic flux in a highly asymmetric one. AMS detector on board of the Space Shuttle in June 1998 has observed primary CR mixed with isotropic secondary quasi-trapped in the Earth magnetic field at low (400 km) altitude and over a large Earth surface (80%). We have developed a code to reconstruct the path (both forward and back in time) of CR inside the magnetosphere (hereafter mags). We realized a complete simulation of the primary CR flux seen by AMS in 1998. In this way we will obtain a relation between the input directions of primary CR outside the mags, and the observed (AMS data) directions. This transfer function F (R, ϑ, φ) is related to the rigidity R of the particle, and to the detecting position.