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<p>Since the discovery of sunspots on the Sun’s surface, solar sunspot numbers (SSN) have been widely used to study solar activity (SA) and its cyclical behaviour. These cycles arise from processes in the Sun’s core and surface, which modulate SA intensity over time. Researchers commonly divide each solar cycle (SC) into distinct phases—minimum, inclining, maximum, and declining—each characterised by different activity levels. However, few studies have systematically characterised SA intensity across these phases, particularly in relation to space weather events and cosmic ray (CR) fluxes, both of which are strongly influenced by SA. This study investigated the variation of SSN, the F10.7 index, solar flare and geomagnetic storm frequencies, and CR particle intensities across SC23 and SC24. SC phases were defined using SSN and F10.7 data, after which all variables were composited by phase and analysed using phase-averaged values. A percentage difference analysis was also conducted to assess variability between the two cycles, while Spearman correlation was employed to evaluate the alignment between SA proxies, space weather, and CR particle fluxes. The results revealed coherent trends in SA proxies across the SC phases, with SC23 showing higher activity levels than SC24. Solar flare frequency aligned closely with SA phases, while geomagnetic storms showed a lag of one to two phases. Proton flux, helium flux, and neutron counts exhibited inverse correlations with SA proxies due to solar wind modulation, although solar energetic particles introduced minor irregularities. The study recommends further use of phase-based approaches in SA research to improve understanding of the Sun’s influence on space weather and CR variability.</p>

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Pattern of solar activity levels and their effects on galactic cosmic ray particle fluxes throughout 23rd and 24th solar cycle

  • 期刊论文

  • 发表日期：

    2026年5月7日

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  • Ahmad Yusof Abdo Jamal,
  • Nurul Shazana Abdul Hamid,
  • Idahwati Sarudin

摘要

Since the discovery of sunspots on the Sun’s surface, solar sunspot numbers (SSN) have been widely used to study solar activity (SA) and its cyclical behaviour. These cycles arise from processes in the Sun’s core and surface, which modulate SA intensity over time. Researchers commonly divide each solar cycle (SC) into distinct phases—minimum, inclining, maximum, and declining—each characterised by different activity levels. However, few studies have systematically characterised SA intensity across these phases, particularly in relation to space weather events and cosmic ray (CR) fluxes, both of which are strongly influenced by SA. This study investigated the variation of SSN, the F10.7 index, solar flare and geomagnetic storm frequencies, and CR particle intensities across SC23 and SC24. SC phases were defined using SSN and F10.7 data, after which all variables were composited by phase and analysed using phase-averaged values. A percentage difference analysis was also conducted to assess variability between the two cycles, while Spearman correlation was employed to evaluate the alignment between SA proxies, space weather, and CR particle fluxes. The results revealed coherent trends in SA proxies across the SC phases, with SC23 showing higher activity levels than SC24. Solar flare frequency aligned closely with SA phases, while geomagnetic storms showed a lag of one to two phases. Proton flux, helium flux, and neutron counts exhibited inverse correlations with SA proxies due to solar wind modulation, although solar energetic particles introduced minor irregularities. The study recommends further use of phase-based approaches in SA research to improve understanding of the Sun’s influence on space weather and CR variability.