Cosmic Ray Inter-Station Correlation Variations as Precursors of Geomagnetic Storms: A Statistical Study and Multi-Parameter Early Warning Framework

TL;DR

This study investigates how cosmic ray inter-station correlation variations can serve as early warning indicators for geomagnetic storms, proposing a multi-level framework validated on historical extreme events.

Contribution

It introduces a novel anisotropy characteristic method and a two-stage early warning framework linking cosmic ray data to geomagnetic storm prediction.

Findings

Significant correlations between GCR parameters and geomagnetic activity.

Precursor signals detectable 48-96 hours before extreme storms.

Validated framework successfully identified precursors for major historical storms.

Abstract

The modulation of galactic cosmic rays (GCRs) by interplanetary disturbances, manifested as Forbush decreases (FDs), has long been recognized as a signature of coronal mass ejection (CME) passages through the heliosphere. While individual FD events have been extensively studied, systematic investigations of how GCR inter-station correlation variations relate to geomagnetic storm (GS) intensity have not been established. Here we analyze the relationship between GCR characteristics (from a global NM network) and GSs, aiming to understand the physical mechanisms of heliospheric disturbances and to develop complementary predictive capabilities beyond existing L1 solar wind monitoring. By applying a newly introduced anisotropy characteristic method alongside correlation analysis to 25 years of hourly NM data (1995-2020, seven stations), we demonstrate significant correlations between GCR parameters and geomagnetic activity. Inter-station relative differences and anisotropy enhancements show distinct precursor signatures depending on storm intensity, with extreme events displaying detectable signals 48-96 hours in advance. Based on these intensity-dependent response patterns, we propose a "two-stage multi-level" early warning framework: mid-term identification (48-96 hr) triggered by sustained anisotropy increases, followed by short-term grading (0-48 hr) based on inter-station relative difference variations and high-latitude flux changes. Validated on the extreme November 2003 and severe August 2018 geomagnetic storms, our approach successfully identifies precursor signals, providing a potential means to extend GS prediction windows.