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109, 1328. : 1965, The passage of energetic particles through interplanetary space, Planet. Space Sci. 13,9. B. : 1978, Phys . Rev. Lett. 40, 38. , Basile G. : 1995, Ph vs. Plasmas 2, 2653 . NON GAUSSIAN AND NON LOCAL TRANSPORT IN THE EARTH'S DISTANT MAGNETOTAIL A. GRECO, G. ZIMBARDO and P. VELTRI Physics Department. University o{ Calabria and lstituto Narionale di Fisica del/a Materia, Unite ' di Cosenia , 1-87036 Arcavacata di Rende. L. TAKTAKISHVILI Ahastumani Astrophysical Observatory, Tiblisi.

In this case , simple picture presented here becomes only the first approximation . 2. R. JOKIPII 2ND-ORDER FERMI ACCELERATION 2nd-Order Fermi acceleration, contained in Equation (5), has an extensive history. It is quite often the mechanism of choice for possible diffuse re-acceleration of cosmic rays in the interstellar medium and in solar flares. Nonetheless, it has at least one considerable disadvantage. It does not produce a power law spectrum with the desired value in a robust way. The shape of the spectrum depends sensitively on the transport parameters in the acceleration region.

The observations, for a variety of species, can be readily accounted for in the present picture, extended to include multiply-charged species. There is no space to discuss this in detail here . 5. Summary and Conclusions The ubiquitous presence of energetic particles in collisionless astrophysical plasmas, and the fact that in many places the energy spectra are power laws with similar indices, suggests that there is a common acceleration for most of the observed cosmic rays . This mechanism appears to be that of diffusive shock acceleration, where the particles are maintained at near isotropy by magnetic scattering, so the diffusive approximation is valid .