26 August 2018 Geomagnetic Storm: Fractal Analysis of Earth Magnetic Field

We perform a systematic and comparative analysis of the fractal dimension estimators as a proxy for data complexity. In particular, we focus on the analysis of the horizontal geomagnetic field components registered by four stations (Belsk, Hel, Sodankylä and Hornsund) at various latitudes during the period of 22 August–1 September, when the 26 August 2018 geomagnetic storm appeared. To identify the fractal scaling and to compute the fractal dimension, we apply and compare three selected methods: structure function scaling, Higuchi, and detrended fluctuation analysis. The obtained results show the temporal variation of the fractal dimension of horizontal geomagnetic field components, revealing differences between their irregularity (complexity). Moreover, the values of fractal dimension seem to be sensitive to the change of physical conditions related to interplanetary shock, the coronal mass ejection, the corotating interaction region, and the high-speed stream passage during the storm development. Especially, a significant decrease in the fractal dimension for all stations is observed immediately following the interplanetary shock, which was not straightforwardly visible in the geomagnetic field components data.