Testing the empirical relationship between Forbush decreases and cosmic ray diurnal anisotropy

TL;DR

This study investigates how interplanetary and geomagnetic magnetic fields influence the relationship between Forbush decreases and cosmic ray diurnal anisotropy, improving understanding of solar-terrestrial interactions.

Contribution

It empirically tests the relationship between Forbush decrease catalogs, diurnal variation, and magnetic field parameters, highlighting the magnetic control over cosmic ray flux reductions.

Findings

Interplanetary magnetic field influences FD evolution.

Geomagnetic Dst field impacts CR flux reductions.

CR diurnal anisotropy affects FD detection accuracy.

Abstract

The abrupt aperiodic modulation of cosmic ray (CR) flux intensity, often referred to as Forbush decrease (FD), plays a significant role in our understanding of the Sun-Earth electrodynamics. Accurate and precise determination of FD magnitude and timing are among the intractable problems in FD-based analysis. FD identification is complicated by CR diurnal anisotropy. CR anisotropy can increase or reduce the number and amplitude of FDs. It is therefore important to remove its contributions from CR raw data before FD identification. Recently, an attempt was made, using a combination of Fourier transformed technique and FD-location machine to address this. Thus, two FD catalogs and amplitude diurnal variation (ADV) were calculated from filtered (FD1 and ADV) and raw (FD2) CR data. In the current work, we test the empirical relationship between FD1, FD2, ADV, and solar-geophysical characteristics. Our analysis shows that two types of magnetic fields-interplanetary (IMF) and geomagnetic (Dst) govern the evolution of CR flux intensity reductions.