Abstract
The objective of this research is to explore the inherent complexities and multifractal properties of the underlying distributions in the daily Planetary K-index time series collected from NOAA Space Weather Prediction Center. In this article, non-stationary and nonlinear characteristics of the signal have been explored using Smoothed Pseudo Wigner–Ville Distribution and Delay Vector Variance algorithms, respectively, while Recurrence Plot, 0–1 test, Recurrence Quantification Analysis and correlation dimension analysis have been applied to confirm and measure the chaos in the signal under consideration. Multifractal detrending moving average has been used to evaluate the multifractality and also recognise the singularities of the signal. The result of these analyses validates the nonstationary and nonlinear characteristics of the Planetary K-index signal, while a significant presence of deterministic chaos in it has also been noticed. It has also been confirmed that the Planetary K-index exhibits multifractal nature with positive persistence. The long-range temporal association and also the large pdf are discovered to be the primary factors that contribute to the multifractal behaviour of the Kp-index.
Highlights
Immense disturbances in the geomagnetic field occur mainly due to the impact of solar storms (like solar flares, solar wind, coronal mass ejection (CME)) on the Earth’s magnetosphere
Whereas the interferences in the frequency domain are attenuated by smoothing the PWVD where it is made to pass through a low-pass filter having window function (t)
Time–frequency spectrum of a stationary signal shows a horizontal line because for stationary signal frequency content does not vary with time, whereas time–frequency spectrum of a nonstationary signal shows discontinuous plot because from spectral point of view a nonstationary signal contains different frequencies at different instants of time
Summary
Immense disturbances in the geomagnetic field occur mainly due to the impact of solar storms (like solar flares, solar wind, coronal mass ejection (CME)) on the Earth’s magnetosphere. This geomagnetic field perturbation, commonly termed as geomagnetic storms, has a significant impact on the backbone of our modern day civilisation, power grids, electronic devices, navigation systems, spacecraft operations and global communications [1, 2]. The magnitude of the geomagnetic storms can be characterised and quantified by the value of Planetary K-index [3]. Kp-index is a measure to quantify the fluctuation of the magnetic field of our planet, it is horizontal component. The official Kp-index is estimated by capturing a weighted average of K-indices from a specified system of geomagnetic observatories, where the K-index is a code that refers to the maximum horizontal component
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