Analysis of fractal properties of horizontal component of Earth’s magnetic field of different geomagnetic conditions using MFDFA

Abstract

Depending on the orientation of the interplanetary magnetic field, solar disturbances induce perturbations in the geomagnetic field as observed by magnetometers on the ground. This study examines the signatures of fractal property of the geomagnetic field’s horizontal component (H time series), as measured by the ground-based magnetometer at Bangui [BNG] (4.33°N, 18.57°E). The Multifractal detrended fluctuation analysis (MF-DFA) method is employed in the study, as it can explore higher-dimensional fractal and multifractal characteristics hidden in the time series. By incorporating MF-DFA, we investigated the changes in the fractal properties of H time series under various geomagnetic conditions, and quantified using Hurst exponent (H) and generalized Hurst exponent h(q). A clear difference in the behaviour of H component during quiet, moderate and intense storm periods is revealed through the analysis of the scaling exponents for different levels of geomagnetic activity. The generalized Hurst exponent h(q) values are found to be higher during the quiet periods, compared to moderate and severe storms periods. It is also observed that both the storm periods and geomagnetically quiet periods are characterized by fractional Brownian motion. The strong q-dependence of h(q) and multifractal scaling exponent τq indicates strong multifractal characteristics of the geomagnetic field data. Thus, the present study reveals that the degree of multifractality is more for the time series of quiet period compared to the one belongs to storm period. Also our results show that the scaling properties of the H time series possess a long-range correlation, showing a long-term persistence of the previous state.