Solar modulation of AMS-02 daily proton and Helium fluxes with modified force field approximation models

TL;DR

This study applies modified force field approximation models to daily AMS-02 cosmic ray data, successfully capturing solar modulation effects on proton and Helium fluxes and validating the models at daily time scales.

Contribution

It introduces and tests modified force field models for daily cosmic ray flux data, improving understanding of solar modulation effects.

Findings

Good agreement between models and data for both proton and Helium fluxes.

Modified FFA models effectively describe daily GCR spectrum variations.

Validation of models at daily time scales enhances cosmic ray modulation understanding.

Abstract

As galactic cosmic rays propagate through the turbulent plasma environment within the heliosphere, they undergo a process of diffusion, drift and energy loss, leading to a notable reduction in their flux. This is the solar modulation impact. Recently, the cosmic-ray experiment AMS-02 published daily fluxes of proton and Helium for the period from May 20, 2011 to October 29, 2019 in the rigidity interval from about 1 to 100 GV, exhibiting fine time structures that correlate with solar wind properties on daily basis. In this work, we employ three different modified force field approximation models to fit the data. By fitting to the daily proton and Helium fluxes, we get the time series of solar modulation potential. We find good agreement of data and model predictions for both proton and Helium with the same parameters in two modified force field approximation models. The results in this study verify that the modified FFA model is a valid parametrization of the GCR spectrum also at daily time scales.