Investigating chaos in solar activity over six solar cycles

Authors

  • Grace Adagba
    Department of Physics, Moses Orshio Adasu University, Makurdi, Benue State, Nigeria
  • Emmanuel Vezua Tikyaa
    Department of Physics, Joseph Sarwuan Tarka University, Makurdi, Benue State, Nigeria
  • Tertsea Igbawua
    Department of Physics, Joseph Sarwuan Tarka University, Makurdi, Benue State, Nigeria
  • Moses Owoicho Audu
    Department of Physics, Joseph Sarwuan Tarka University, Makurdi, Benue State, Nigeria

Keywords:

Solar cycle, Sunspot number, Equivalent planetary amplitude, Solar radio flux, Chaos

Abstract

In this work, nonlinear dynamical characterization of selected geospace variables was undertaken by analyzing temporal chaotic trends in daily sunspot number (SSN), equivalent planetary amplitude (Ap), and solar radio flux (F10.7obs) data over six solar cycles (19--24). The nonlinear analysis tools used were correlation dimension, Lyapunov exponents, approximate entropy, and the Gottwald--Melbourne 0--1 test. The results show that the Lyapunov exponents, correlation dimension, and 0--1 test values indicate the presence of low-dimensional deterministic chaos in SSN, Ap, and F10.7obs. The Lyapunov exponent values were positive, the correlation dimension values fell within the range 2.1 < D2 < 2.3, the surrogate significance test returned positive values for all three parameters, and the 0--1 test results were very close to one (all >0.99). The Hurst values were between 0.8 and 1, indicating persistence and long-term autocorrelation. Based on the correlation dimension and Lyapunov exponent values, the chaoticity was affirmed as Ap < SSN < F10.7obs. Chaotic trends across the solar cycles showed that the degree of chaos in all three solar-cycle parameters increased from cycle 19 to cycle 24. This increase is attributed to small perturbations in interior plasma flow, shear in the axis of rotation, and variation in the strength and orientation of the Sun's geomagnetism, which are amplified over time, as evident in the decrease in the mean SSN (129--49) and increase in the signal-to-noise ratio (0.84--0.96). These processes lead to increased fluctuations in the amplitude and periodicity of solar activity from one solar cycle to another.

Dimensions

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Published

2026-07-02

How to Cite

Investigating chaos in solar activity over six solar cycles. (2026). African Scientific Reports, 5(2), 517. https://doi.org/10.46481/asr.2026.5.2.517

Issue

Volume 5, Issue 2, August 2026

Section

PHYSICS SECTION
Copyright & Licensing

Copyright (c) 2026 Grace Adagba, Emmanuel Vezua Tikyaa, Tertsea Igbawua, Moses Owoicho Audu

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

How to Cite

Investigating chaos in solar activity over six solar cycles. (2026). African Scientific Reports, 5(2), 517. https://doi.org/10.46481/asr.2026.5.2.517

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