Influence of Sunspot Numbers and Solar Radio Flux on Geomagnetic Storm Activity during Solar Cycles 24 and 25

Abstract

This study systematically investigates the complicated link between solar activity indicators, specifically sunspot numbers (SSN) and solar radio flux (F10.7), and the occurrence of geomagnetic storms during Solar Cycles 24 and 25. The primary objective is to quantify the influence of these solar parameters on Earth's magnetospheric disturbances. The methodology involved a detailed analysis of 231 peak Disturbance Storm Time (Dst) events (P), 214 initial phase (P-I) geomagnetic storm events, and 201 recovery phase(P-R) geomagnetic storm events, all identified by a Dst threshold of ≤ -50 nT, covering the period from January 2008 to June 2024.

Statistical analysis, primarily through the calculation of Pearson correlation coefficients, revealed robust positive correlations. Peak Dst events exhibited correlation coefficients of 0.67 with sunspot numbers and 0.72 with solar radio flux. Similarly, geomagnetic storm events during the initial phase showed strong positive correlations with sunspot numbers (r = 0.69) and solar radio flux (r = 0.73). A comparable positive correlation was also observed during the recovery phase, with coefficients of 0.69 for sunspots and 0.73 for solar radio flux. A particularly striking finding was the exceptionally high correlation of 0.98 between the yearly average sunspot number and yearly average solar radio flux, underscoring the profound interconnectedness of these two solar parameters.

These findings highlight the significant predictive potential of sunspot numbers and solar radio flux in forecasting geomagnetic storm activity. The consistent strength of these correlations across different storm phases suggests that solar activity levels exert a sustained influence throughout the entire evolution of a geomagnetic disturbance, not merely its onset. Furthermore, the comparative analysis of Solar Cycle 24, which was historically weak, and the rapidly rising Solar Cycle 25 offers important clues about the evolving character of solar magnetic variability and its implications for space weather dynamics. The observed resurgence of activity in Cycle 25 implies a heightened likelihood of geo-effective space weather events compared to the preceding cycle.