Scaling Features of Diurnal Variation of Galactic Cosmic Rays

Abstract

We analyze the scaling properties of the diurnal variation of galactic cosmic rays (GCRs) in Solar Cycle 24 and the solar minima between Solar Cycles 23/24 and 24/25 for 2007 – 2019 based on the count rates of the Oulu, Newark, Hermanus, and Potchefstroom neutron monitors. The scaling features of the GCR diurnal variation are studied by evaluating the Hurst exponent, a quantitative parameter used as an indicator of the state of the randomness of a time series. We estimate the Hurst exponents for GCR diurnal-variation parameters amplitude and phase using structure-function and detrended-fluctuation-analysis methods. Results show that the Hurst exponents for the GCR diurnal variation vary in the range from $\approx0.3$ ≈ 0.3 to $\approx0.9$ ≈ 0.9 , with a general tendency of being systematically above 0.5. It suggests that the GCR diurnal variation reveals a more persistent structure than Brownian motion. However, the time series of GCR diurnal-variation amplitude and phase evolve from a more persistent structure in the solar minimum between Solar Cycles 23/24 in 2007 – 2009 to a more random character in and near the solar maximum 2012 – 2014. This observation seems to be in agreement with the general configuration of the heliosphere through the 11-year solar-activity cycle. Moreover, the temporal profile of the Hurst exponent for GCR diurnal amplitude and phase around the beginning of the solar minimum between Solar Cycles 24/25 (2018 – 2019) differs from the solar minimum between Solar Cycles 23/24 in 2007 – 2009, suggesting a dependence on solar-magnetic polarity. These findings could shed more light on GCR particle transport in the turbulent heliosphere over the solar cycle.

Fractal Dimension Analysis of Earth Magnetic Field during 26 August 2018 Geomagnetic Storm

“…In this work, basing on the review of literature and continuing our previous studies [32,45], we initially compared a few methods: the Katz algorithm [11], which revealed discriminating power [32,38], its modifications [46,47], Higuchi method [12], Structure Function scaling [18,[48][49][50], and Detrended Fluctuation Analysis [15,51].…”

Decades of Diurnal Anisotropy: Unravelling the Time of Maximum of Diurnal Anisotropy

“…Kumar (1998) revealed that a shift to early hours during specific periods is related to the polarity of the solar magnetic field, Park (2018) confirming a 22-year periodicity. The studies of (Modzelewska et al, 2021;Park, 2018) have shown that the diurnal phase tends to shift towards later hours during the maximum solar activity years compared with the minimum solar activity years. Furthermore, Okiyi et al (2017) suggested that phase variation has components of both 22-year and 11-year cycles, influenced by solar polar magnetic field reversal and interplanetary magnetic field strength changes associated with sunspot cycles.…”

Persistent Behavior in Solar Energetic Particle Time Series

“…More recently, Pavlos et al (2019) employed Hurst analysis for the study of the energetic ion intensity and magnetic field for the description (and understanding) of small-scale magnetic island structures in the solar wind of typical size 0.01-0.001 au at 1 au. The Hurst method was recently applied by Modzelewska et al (2021) in the study of galactic cosmic rays based on data obtained by the Oulu, Newark, Hermanus, and Potchefstroom neutron monitors. To understand the processes in the near-Earth electromagnetics, the Hurst exponent, together with other complex system methods, has also been reviewed by Balasis et al (2023).…”