Intermittency and multifractional Brownian character of geomagnetic time series

Abstract

The Earth's magnetosphere exhibits a complex behavior in response to the solar wind conditions. This behavior, which is described in terms of mutifractional Brownian motions, could be the consequence of the occurrence of dynamical phase transitions. On the other hand, it has been shown that the dynamics of the geomagnetic signals is also characterized by intermittency at the smallest temporal scales. Here, we focus on the existence of a possible relationship in the geomagnetic time series between the multifractional Brownian motion character and the occurrence of intermittency. In detail, we investigate the multifractional nature of two long time series of the horizontal intensity of the Earth's magnetic field as measured at L'Aquila Geomagnetic Observatory during two years (2001 and 2008), which correspond to different conditions of solar activity. We propose a possible double origin of the intermittent character of the small-scale magnetic field fluctuations, which is related to both the multifractional nature of the geomagnetic field and the intermittent character of the disturbance level. Our results suggest a more complex nature of the geomagnetic response to solar wind changes than previously thought

Jensen‐Shannon Complexity and Permutation Entropy Analysis of Geomagnetic Auroral Currents

“…Following the work of Balasis et al (), Consolini et al (), and Osmane et al (), our study also provides additional means to characterize large‐scale and small‐scale fluctuations originating in different physical processes. In a statistical study covering 17 years of OMNI data, Osmane et al () showed that probability distribution functions of AL responded in a nontrivial yet coherent fashion to various solar wind properties and ultralow frequency fluctuation amplitudes.…”

On the local Hurst exponent of geomagnetic field fluctuations: Spatial distribution for different geomagnetic activity levels

“…For this reason, in DMA technique we choose a time window of 801 points to ensure an optimal noise/signal ratio in determining the local Hurst exponent. It has been shown by Consolini et al [] using a synthetic signal of 5·10 5 points, that for this time window (801 points) the local Hurst exponent estimated using DMA technique can be determined with an average precision equal to 10%. Thus, the selected time window is a good compromise between the time domain of the magnetic fluctuations that we can analyze and the need to have sufficient statistical power for the local Hurst exponent estimation.…”

Forecasting geomagnetic activity at monthly and annual horizons: Time series models

“…This type of variability has been characterized as fractal in prior analyses (Consolini et al, 2013), and is typical of multifractal processes (Lovejoy and Schertzer, 2013). In this respect, some studies have argued that solar activity may be chaotic, with variations tracing back to a small number of deterministic attractors (Hansen and Willson, 1997;Solanki and Krivova, 2011;Feynman and Ruzmaikin, 2011).…”