Heliospheric regimes governing Forbush decreases revealed by multiscale analysis of cosmic rays

Abstract

We investigate the dynamical structure of galactic cosmic ray intensity using multiscale analysis applied to daily records from 16 neutron monitor stations over 2010--2025. The objective is to determine whether large Forbush decreases are associated with identifiable statistical states of heliospheric modulation. We identify a statistically distinct heliospheric regime---characterised by elevated long-range persistence and reduced natural-time variance---in which large Forbush decreases are significantly more likely. Multifractal detrended fluctuation analysis and natural time analysis are applied in a rolling framework to characterize long-range correlations and event-order dynamics. The results show that persistent long-range correlations and multifractal structure are universal across the global network. A coherent evolution driven by the solar cycle is observed, with reduced persistence during the 2019--2020 solar minimum and enhanced organization during active periods. Across nine major Forbush decreases, 78\% occur during intervals of elevated persistence and reduced natural-time variance, indicating a distinct heliospheric regime associated with an increased likelihood of events. No significant relationship is found between these metrics and event magnitude, confirming that the signal reflects a statistical state rather than a deterministic precursor. The combined analysis demonstrates that multiscale and natural-time approaches provide complementary information, offering a more complete characterization of heliospheric dynamics and reframing Forbush decreases as regime-dependent phenomena rather than isolated stochastic events.