Testing the Effect of Solar Wind Parameters and Geomagnetic Storm Indices on Galactic Cosmic Ray Flux Variation with Automated-Selected Forbush Decreases

TL;DR

This study introduces an automated method for detecting Forbush decreases in cosmic ray data and investigates their relationship with solar wind parameters and geomagnetic storm indices, revealing significant correlations.

Contribution

The paper presents a new automated software tool for identifying FDs and validates its effectiveness by analyzing their correlation with solar wind and geomagnetic data.

Findings

Significant linear relationship between large FDs and solar wind parameters.

Automated FD detection aligns with known solar-terrestrial interaction patterns.

230 FDs identified from 1998-2002 data.

Abstract

Forbush decrease (FD), discovered by Scott E. Forbush about 80 years ago, is reffered to as the non-repetitive short-term depression in galactic cosmic ray (GCR) flux, presumed to be associated with large-scale perturbations in solar wind and interplanetary magnetic field (IMF). It is the most spectacular variability in the GCR intensity which appear to be the compass for investigators seeking solar-terrestrial relationships. The method of selection and validation of FD events are very important to cosmic ray scientists. We have deployed a new computer software to determine the amplitude and timing of FDs from daily-averaged cosmic ray (CR) data at OULU neutron monitor station. The code selected 230 FDs between 1998 and 2002. In an attempt to validate the new FD automated catalog, the relationship between the amplitude of FDs, and IMF, solar wind speed (SWS) and geomagnetic storm indices (Dst, kp, ap) is tested here. A two-dimensional regression analysis indicates significant linear relationship between large FDs (CR(\%) $\leq-3$) and solar wind data and geomagnetic storm indices in the present sample. The implications of the relationship among these parameters are discussed.