Interplanetary cosmic ray radial gradients with steady state modulation models

We have used steady state modulation models of increasing complexity, with emphasis on drift models, to establish to what extent these models can simulate the observed cosmic ray integral radial gradient (energy≥60--70 MeV/nucleon) in the heliosphere from 1977 to 1986. Special attention has been given to the apparent asymmetric behavior of the radial gradient with respect to the recent interplanetary magnetic field polarity reversal, and the remarkable constant radial gradient for the years 1977--1982. Instead of using differential intensities at specific energies, we presented integral radial gradients calculated from the computed integral intensities which made comparison with observations more realistic. We found that nondrift models had difficulties producing constant radial gradients over several years of increasing solar activity, because these models depend primarily on changes of the radial diffusion coefficient K/sub r//sub r/ to simulate an 11-year cycle and therefore produce, in general, radial gradients symmetric with respect to solar maximum activity. Making these models independent of changes in K/sub r//sub r/ needs, in our opinion, unrealistic changes in the conventional modulation parameters