Simulations of galactic and anomalous cosmic ray transport in the heliosphere

The companion paper of Fisk (1999) in this volume convincingly argues that the theory of cosmic ray transport in the heliosphere has probably been complete for almost three decades. The outstanding problem is to find the magnitude, spatial, and energy dependence of the convection, diffusion, drift, adiabatic cooling, and acceleration mechanisms. This problem can be addressed in two complementary ways: the relevant parameters can be calculated from theory, or the observed particle spectra can be used to deduce them. This paper emphasises the second approach, i.e., we review to what extent one is able to fit cosmic ray observations self-consistently with a single set of modulation parameters. For this purpose we mainly concentrate on model fits to the intensity spectra of cosmic ray protons, helium, and oxygen as observed during the solar minimum periods of 1987 and 1997. The main results are that: (1) the scattering parameters deduced from the particle spectra broadly fall in the same range as the newest values derived from theory, but (2) the separate sets of scattering parameters needed to simulate the 1987 and 1997 solar minimum spectra differ so much from one another that it is unlikely that the final solution has been found.