Modeling Albedo Particles Distribution at the near Earth Region

A recent space experiment, Alpha Magnetic Spectrometer (AMS), had measured cosmic rays at altitude 400km. An unexpected result is a secondary spectrum at below cutoff. Their energy ranges from 0.1 to 6 GeV. These particles, called albedo particles, originate from atmosphere and rebound to space. They stay at space in very short time. These albedo particles compose a high energetic part of space radiation but little knowledge of them is known. They have energy near the minimum ionization and have greatest penetrating power. A good model of these high energetic particles is essential to the modeling of radiation dosage in space. To reach this goal, computer simulation code of albedo particle fluxes covering areas outside AMS flight path is developing. The major difficulty is the massive amount of computer simulation. For re-tracing AMS data, the estimate time is approximately 500 days for a Pentium III 500MHz computer. To assess the possibility to reduce computing time, we adopt adiabatic invariants method to trace particles in the IGRF field model. Our previous studies have used this method to simulate energetic particles­Ý equatorial trajectories for VIP4 model of Jupiter at much less computing time. The global distribution of fluxes would be deduced from the available AMS data.