Variation of the cosmic ray intensity in an 11-yr solar activity cycle: Experiment and theory

To study long-term variations of the cosmic ray intensity in a wide energy range, a basic model of the modulation of cosmic rays in the heliosphere has been developed at the Institute of Cosmophysical Research and Aeronomy, Siberian Branch, Russian Academy of Sciences. The model involves only one free modulation parameter, the ratio of the regular magnetic field to the turbulent field. It can be used to describe variations of the cosmic ray intensity in a wide energy range of $0.1$ to $100$ GeV. Attempts have been made to most correctly describe the features of the behavior of the cosmic ray intensity in several solar activity cycles.