Simulation of Galactic Cosmic Ray Proton Fluxes With the Daily Modulation Parameter: Validation With AMS‐02 Data for 2011–2019

Abstract The flux of galactic cosmic rays (GCRs) is modulated by solar activity on different time scales. This is often described with the force‐field approximation via the single variable parameters of the modulation parameter, which formally corresponds to the average rigidity loss of GCR particles in the heliosphere. The force‐field approximation is usually assumed to work properly only for periods of a solar rotation (27 days) or longer. However, daily values of the modulation parameter have been constructed based on ground‐based neutron monitor (NM) data suggesting that this approach might work reasonably well also on shorter time scales. Here we check this by simulating the daily GCR proton fluxes using the force‐field approach and the daily modulation parameter reconstructions, and confronting them with the daily proton‐flux measurements by the AMS‐02 onboard the International Space Station. A polynomial regression between the simulated and measured fluxes is proposed for longer‐term analyses and interpolations. For mid‐rigidities from 5–15 GV, the agreement is accurate within and slightly worsens toward higher rigidities, likely because of smaller statistics. We also found a lingering solar‐cycle trend at lower energies between the data and the model and the effect of the solar magnetic field polarity. These findings can be used for the utilization of the force‐field approach for short‐term variations.