Models of Galactic Cosmic-Ray Spectrum during the Solar Cycle

The basic processes affecting the cosmic ray (CR) transport in the heliosphere are combined in Parker's transport equation. However, adequate description of the relation between the modulation processes in the heliosphere and the profiles of the modulated GCR spectrum is a difficult task because the theoretical models should consider many parameters whose values are not known throughout the heliosphere. That is why the use of empirical and theoretical approximations is recommended, especially for calculation of CR's atmospheric effects and for practical tasks. A brief review is given of the most often used models for interpretation of cosmic ray data and prediction of particle fluxes. The force-field and diffusion-convection approximations to the cosmic ray transport equation, Moscow State University (MSU) model, Nagashima and Morishita, Badhwar and O'Neill's models, as well as Cosmic Ray Spectrum Approximation (CRSA) model, are discussed in the paper. The CRSA is compared to the Nagashima and Morishita's model equation and dependence between CRSA model parameters and time-lagged solar-heliospheric parameters for a given rigidity P-xi is derived.