Abstract
This study investigates the dynamic modulation of Galactic Cosmic Rays (GCRs) in response to solar activity parameters during the ascending-to-peak phase of Solar Cycle 25, covering the period from January 1 to March 17, 2025 (76 consecutive days). High-resolution daily datasets from a mid-latitude neutron monitor (Athens, ATHN) and a polar neutron monitor (South Pole, SOPO) were analyzed alongside three solar-interplanetary proxies: Sunspot Number (SSN), Interplanetary Magnetic Field magnitude (IMF), and a Geocentric Solar Ecliptic Bz orientation proxy (GSE). Both linear (Pearson) and non-linear/monotonic (Spearman) correlation analyses were performed across all parameter pairs at each station. The results reveal a pronounced, statistically meaningful inverse relationship between polar cosmic ray flux and solar activity (r SOPO, SSN = −0.44, ρ SOPO, SSN = −0.38), consistent with solar modulation and Forbush-type depression behavior at high magnetic latitudes. Mid-latitude observations, by contrast, show weaker direct linear dependence on sunspot number but a markedly stronger non-linear coupling with interplanetary magnetic field orientation (ρ ATHN, GSE = 0.70), pointing to rigidity-cutoff-dependent access effects rather than simple solar-cycle scaling. Together, these findings illustrate how geomagnetic latitude governs the physical mechanism direct solar activity modulation at the poles versus magnetic-topology-dependent access at mid-latitudes by which the heliosphere regulates cosmic ray ingress into the Earth’s atmosphere.
KEYWORDS
Galactic Cosmic Rays, Heliospheric Modulation, Solar Activity, Sunspot Number, Interplanetary Magnetic Field, Solar Cycle 25.
Shiva Soni
Poornima University Jaipur-302022, Rajasthan, India