A comprehensive set of predictions using a newly developed, axially symmetric, steady state, drift model with a wavy neutral sheet is compared with data obtained during an entire 11 yr solar modulation cycle from 1976 to 1987. The model accurately predicts the 1976 modulated proton and helium spectra starting with realistic interstellar spectra for these species, but only when drift effects are somewhat reduced. For 1981-1987, the proton intensities with energy of 60 MeV and higher and E = 120-227 MeV observed by IMP, and those predicted by this model as a function of neutral sheet tilt agree fairly well. These results suggest that the correlation between intensity and the observed tilt reported by other groups has a theoretical explanation in terms of a drift and a wavy neutral sheet picture. The model can explain many of the observed features of the 11 yr cycle, showing that drift together with the wavy neutral sheet probably play a significant role.
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Webber et al. (1990) studied this question.