Evidence for a Time Lag in Solar Modulation of Galactic Cosmic Rays

TL;DR

This study presents a simple model linking solar activity to cosmic-ray flux variations, revealing an 8-month delay in solar modulation effects, enabling better forecasting of cosmic-ray levels near Earth.

Contribution

The paper introduces a predictive model of solar modulation based on solar activity parameters, demonstrating a quantifiable time lag in cosmic-ray flux response.

Findings

Identified an 8.1-month time lag in solar modulation of cosmic rays.

Developed a model predicting cosmic-ray spectra from solar activity data.

Validated the model with space mission data.

Abstract

The solar modulation effect of cosmic rays in the heliosphere is an energy-, time-, and particle-dependent phenomenon which arises from a combination of basic particle transport processes such as diffusion, convection, adiabatic cooling, and drift motion. Making use of a large collection of time-resolved cosmic-ray data from recent space missions, we construct a simple predictive model of solar modulation which depends on direct solar-physics inputs: the number of solar sunspots and the tilt angle of the heliospheric current sheet. Under this framework, we present calculations of cosmic-ray proton spectra, positron/electron and antiproton/proton ratios and their time dependence in connection with the evolving solar activity. We report evidence for a time-lag $\Delta{T}=8.1\pm\,1.2$ months, between solar activity data and cosmic-ray flux measurements in space, which reflects the dynamics of the formation of the modulation region. This result enables us to forecast the cosmic-ray flux near Earth well in advance by monitoring solar activity