Modeling and experimental study of the 27-day variation of galactic cosmic-ray intensity for a solar-wind velocity depending on heliolongitude

TL;DR

This study presents a 3-D model of the 27-day variation of galactic cosmic ray intensity incorporating solar wind velocity changes with heliolongitude, successfully matching observed data.

Contribution

The paper introduces a novel 3-D model that accounts for spatially varying solar wind velocity and magnetic fields to explain GCR intensity variations.

Findings

Model predictions correlate with observed data (correlation coefficient 0.80).

The model accurately reproduces the 27-day GCR variation during the studied period.

Incorporating variable solar wind improves understanding of cosmic ray modulation.

Abstract

We develop a three dimensional (3-D) model of the 27-day variation of galactic cosmic ray (GCR) intensity with a spatial variation of the solar wind velocity. A consistent, divergence-free interplanetary magnetic field is derived by solving the corresponding Maxwell equations with a variable solar wind speed, which reproduces in situ observed experimental data for the time interval to be analyzed (24 August 2007-28 February 2008). We perform model calculations for the GCR intensity using the variable solar wind and the corresponding magnetic field. Results are compatible with experimental data; the correlation coefficient between our model predictions and observed 27-day GCR variation is 0.80 0.05.