  Galactic cosmic rays (CRs) inside the heliosphere are affected by solar
modulation. To investigate this phenomenon and its underlying physical
mechanisms, we have performed a data-driven analysis of the temporal dependence
of the CR proton flux over the solar cycle. The modulation effect was modeled
by means of stochastic simulations of cosmic particles in the heliosphere. The
model were constrained using measurements of CR protons made by AMS-02 and
PAMELA experiments on monthly basis from 2006 to 2017. With a global
statistical analysis of these data, we have determined the key model parameters
governing CR diffusion, its dependence on the particle rigidity, and its
evolution over the solar cycle. Our results span over epochs of solar minimum,
solar maximum, as well as epochs with magnetic reversal and opposite
polarities. Along with the evolution of the CR transport parameters, we study
their relationship with solar activity proxies and interplanetary parameters.
We find that the rigidity dependence of the parallel mean free path of CR
diffusion shows a remarkable time dependence, indicating a long-term
variability in the interplanetary turbulence that interchanges across different
regimes over the solar cycle. The evolution of the diffusion parameters show a
delayed correlation with solar activity proxies, reflecting the dynamics of the
heliospheric plasma, and distinct dependencies for opposite states of magnetic
polarity, reflecting the influence of charge-sign dependent drift in the CR
modulation.
