Solar and Interplanetary Determinants of Long-term Solar Modulation of Cosmic-Ray Intensity for Median Rigidities of 11-107 GV

Abstract

We investigate the long-term modulation of cosmic-ray (CR) intensity across median rigidities from 11 to 107 GV using over four decades (1980-2023) of data from neutron monitors (NMs) and muon detectors (MDs). The analysis incorporates global NM stations and the Nagoya Multi-Directional Muon Telescope to evaluate the influence of key heliospheric parameters: interplanetary magnetic field (IMF) strength, heliospheric current sheet tilt angle (TA), and solar wind (SW) speed. Results reveal pronounced rigidity-dependent modulation patterns. Lower-rigidity NMs exhibit stronger sensitivity to heliospheric conditions, driven largely by IMF and TA, consistent with diffusion- and drift-dominated transport. In contrast, higher-rigidity MDs show reduced modulation amplitudes, with IMF remaining the dominant influence and SW gaining relative importance as drift effects diminish. These findings provide new insight into the energy-dependent roles of heliospheric drivers in CR modulation and offer a robust framework for advancing space weather prediction and heliospheric transport modeling.