Multi-Scale Variability of Solar Wind Turbulence and Its Influence on Near-Earth Space Weather

Abstract

Solar wind turbulence plays a fundamental role in governing the transfer of mass, momentum, and energy from the Sun to the Earth\'s magnetosphere. Variations in solar wind plasma and interplanetary magnetic field (IMF) parameters occur over a broad range of temporal scales, from minutes to several days, and significantly influence near-Earth space weather conditions. Understanding the multi-scale nature of these fluctuations is essential for improving the prediction of geomagnetic disturbances and their associated impacts on technological systems.This study investigates the temporal variability of solar wind turbulence and its relationship with geomagnetic activity during Solar Cycle 25. Hourly solar wind parameters, including solar wind speed, proton density, temperature, and IMF components, are analyzed using data obtained from the OMNI database. Multi-scale characteristics of solar wind turbulence are examined through statistical and spectral techniques, including power spectral density and wavelet analysis. Geomagnetic activity is assessed using the Disturbance Storm Time (Dst), planetary K-index (Kp), and Auroral Electrojet (AE) indices.The analysis reveals that enhanced levels of solar wind turbulence are frequently associated with periods of increased geomagnetic activity. Significant fluctuations in IMF Bz and solar wind velocity contribute to efficient solar wind–magnetosphere coupling, resulting in stronger geomagnetic storms and substorm activity. Wavelet analysis identifies distinct periodicities corresponding to short-term and intermediate-scale turbulent processes, while correlation analysis demonstrates statistically significant relationships between turbulence intensity and geomagnetic indices. The results further indicate that turbulent solar wind structures can serve as important precursors to space weather disturbances.The findings highlight the critical role of multi-scale solar wind turbulence in modulating near-Earth space weather and provide valuable insights into the physical mechanisms responsible for geomagnetic variability. This work contributes to ongoing efforts aimed at improving space weather forecasting and understanding Sun–Earth interactions during the current solar cycle.

Introduction

This study investigates solar wind turbulence and its impact on near-Earth space weather during Solar Cycle 25 (2020–2025). The solar wind, a continuous stream of charged particles emitted by the Sun, strongly influences Earth's magnetosphere, ionosphere, and thermosphere, causing phenomena such as geomagnetic storms, auroras, and satellite disruptions.

The research builds on foundational work by scientists such as Eugene Parker, who first explained the existence of the solar wind, and later studies that identified turbulence as a key characteristic of heliospheric plasma. Solar wind turbulence arises from sources including coronal holes, active regions, coronal mass ejections (CMEs), and stream interaction regions, producing fluctuations across multiple temporal and spatial scales.

The literature review highlights major developments in turbulence theory, including Andrey Kolmogorov’s energy cascade model and later magnetohydrodynamic (MHD) turbulence studies. Previous research established that solar wind turbulence exhibits anisotropy, intermittency, and scale-dependent behavior, while also playing a major role in solar wind–magnetosphere coupling through magnetic reconnection processes.

Methodology

The study uses:

• Solar wind data from the OMNI Database.
• Geomagnetic indices including:
  • Dst Index
  • Kp Index
  • AE Index
• Solar wind parameters such as velocity, proton density, temperature, magnetic field components (Bx, By, Bz), and dynamic pressure.

Data undergo quality control, interpolation, normalization, and hourly standardization. Turbulence intensity is measured using statistical metrics like variance and standard deviation.

Analysis Techniques

The study applies:

• Power Spectral Density (PSD) using Fast Fourier Transform (FFT) to identify dominant turbulence frequencies and energy distributions.
• Continuous Wavelet Transform (CWT) to analyze time-varying and non-stationary turbulence structures.
• Correlation analysis to examine relationships between turbulence intensity and geomagnetic activity indicators.

Key Findings

• Solar wind parameters during Solar Cycle 25 exhibited significant fluctuations, confirming the presence of persistent turbulent structures.
• Turbulence occurred across multiple scales, from hours to several days.
• Enhanced turbulence was associated with increased geomagnetic activity and stronger solar wind–magnetosphere coupling.
• Southward IMF Bz conditions, high solar wind speeds, and disturbed plasma conditions contributed to stronger geomagnetic storms.
• Multi-scale spectral and wavelet analyses provided valuable insight into turbulence evolution and its geoeffective consequences.

Conclusion

The present investigation examined the multi-scale variability of solar wind turbulence and its influence on near-Earth space weather during Solar Cycle 25. Solar wind turbulence represents one of the most important processes governing the transport of mass, momentum, and energy throughout the heliosphere. Understanding how turbulent fluctuations affect the Earth\'s magnetosphere is essential for improving space weather forecasting and mitigating the impacts of geomagnetic disturbances on technological systems. By analyzing solar wind speed, interplanetary magnetic field (IMF) Bz, and geomagnetic activity represented by the Dst index, this study provides valuable insight into the complex coupling mechanisms operating between the Sun and Earth. The results demonstrated that solar wind conditions exhibit significant variability across a wide range of temporal scales. Variations in solar wind speed and IMF Bz revealed the presence of turbulent structures embedded within the solar wind plasma. These fluctuations were observed throughout the study period and were frequently associated with enhanced geomagnetic activity. The temporal analysis showed that intervals characterized by elevated solar wind speed and southward IMF Bz were often followed by pronounced decreases in the Dst index, indicating intensified geomagnetic storm conditions. Such observations confirm the critical role of solar wind dynamics in regulating magnetospheric behavior. The wavelet-based investigation further highlighted the multi-scale nature of solar wind turbulence. Enhanced wavelet power was observed during several intervals, indicating the presence of intermittent turbulent activity and nonlinear energy transfer processes. These results support the theoretical framework of magnetohydrodynamic turbulence proposed in earlier studies and demonstrate that turbulence within the solar wind is neither stationary nor uniformly distributed. Instead, turbulent energy is concentrated within localized intervals that may significantly influence the geoeffectiveness of solar wind structures. The identification of these intervals provides additional information beyond traditional solar wind monitoring techniques and contributes to a more comprehensive understanding of space weather variability. Correlation analysis revealed statistically meaningful relationships between solar wind parameters and geomagnetic activity. The moderate negative correlation between solar wind speed and Dst suggests that stronger solar wind conditions generally correspond to more intense geomagnetic disturbances. Similarly, the observed relationship between IMF Bz and Dst emphasizes the importance of magnetic field orientation in controlling solar wind–magnetosphere coupling efficiency. These findings indicate that both plasma properties and magnetic field fluctuations must be considered when evaluating the potential impact of solar wind disturbances on the near-Earth environment. The study also demonstrates the usefulness of combining temporal analysis, wavelet techniques, and statistical methods for investigating solar-terrestrial interactions. While conventional space weather studies frequently focus on large-scale solar wind structures such as coronal mass ejections and high-speed streams, the present results indicate that embedded turbulent fluctuations can substantially modify magnetospheric responses. Consequently, turbulence diagnostics should be incorporated into future forecasting models to improve the prediction of geomagnetic storms and other space weather hazards. From an applied perspective, improved understanding of solar wind turbulence is important for the protection of satellites, communication systems, navigation networks, aviation operations, and power grid infrastructure. As human dependence on space-based technologies continues to increase, accurate forecasting of space weather events becomes increasingly important. The findings presented in this study contribute to ongoing efforts aimed at developing more reliable predictive capabilities for operational space weather services. Future investigations should extend the present analysis by incorporating longer observational intervals, additional geomagnetic indices such as AE and Kp, and advanced turbulence diagnostics derived from higher-resolution measurements. The use of spacecraft observations from multiple heliospheric locations may also provide a more detailed understanding of turbulence evolution and propagation. Furthermore, machine-learning approaches combined with turbulence indicators may offer promising opportunities for improving space weather forecasting accuracy. Overall, this study confirms that solar wind turbulence is a fundamental component of solar–terrestrial interactions and plays a significant role in shaping near-Earth space weather conditions. The observed relationships between turbulent solar wind fluctuations, magnetic field variability, and geomagnetic activity demonstrate the importance of considering multi-scale processes when investigating the dynamics of the heliosphere and the terrestrial magnetosphere. The results contribute to a growing body of evidence emphasizing that turbulence is not merely a background feature of the solar wind but an active driver of space weather variability.

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Copyright

Copyright © 2026 Sunil Kumar Pathak, Mukta Tripathi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.