Probing solar modulation of AMS-02 time-dependent D, $^3$He and $^4$He fluxes with modified force field approximation

TL;DR

This study employs modified force-field approximations to analyze AMS-02 time-dependent cosmic-ray isotope fluxes, validating the models and forecasting future fluxes based on solar modulation parameters.

Contribution

It introduces and validates modified force-field approximation models with rigidity-dependent potentials for solar modulation of cosmic-ray isotopes.

Findings

All isotopes can be fitted with the same solar modulation parameters.

Modified FFA models are validated as effective parametrizations.

Forecasts of daily isotope fluxes from 2011 to 2020 are provided.

Abstract

The AMS-02 experiment recently published time-dependent fluxes of deuterons (D) from May 2011 to April 2021, divided into 33 periods of four Bartels rotations each. These temporal structures are associated with solar modulation. In this study, three modified force-field approximation are employed to examine the long-term behavior of cosmic-ray (CR) isotopes such as D, $^3$He, and $^4$He, as well as the ratios D/$^3$He and $^3$He/$^4$He. The solar modulation potential is rigidity-dependent for these modified force-field approximation models. Due to the unknown local interstellar spectrum (LIS) for these isotopes, we utilize the Non-LIS method for solar modulation. By fitting to the AMS-02 time-dependent fluxes, we derive the solar modulation parameters. Our findings prove the assumption in literature that all isotopes can be fitted using the same solar modulation parameters and it shown that the modified FFA models are validated parametrization for solar modulation. Based on these, we forecast the daily fluxes of D, $^3$He and $^4$He from 2011 to 2020.