“Multi-scale nature of the high-latitude magnetic field fluctuations”

Abstract

We analyze the properties of the geomagnetic field fluctuations during a period (13-30 March 2015) characterized by different geomagnetic activity levels including the strongest geomagnetic storm of XXIV solar cycle occurred on 17 March 2015. The one minute values of theX and Y componentsof the geomagnetic field recorded simultaneously in the Northern and Southern hemispheres are analyzed. The Empirical Mode Decomposition (EMD) method is applied to the selected dataset in order to separate short timescale (𝜏<200 min) and long timescale(𝜏>200 min) magnetic field fluctuations, which have been suggested to be related to different physical processes. It has been shown that while magnetic fluctuations at long timescales (𝜏>200 min) show a large degree of correlation between solar wind parameters and magnetospheric dynamics proxies, at short timescales (𝜏<200 min) they are essentially related to internal magnetospheric processes and seem to be not directly driven by interplanetary changes. Daily maps of the fast and slow magnetic field fluctuations during the selected period are analyzed to investigate the contributionsto the recorded magnetic signal related to the different magnetospheric processes and their dependence on the geomagnetic activity level. A comparison between the two hemispheres isalso shown.