An investigation of the 1/fα long-range fluctuations in short-term time variability of ULF geomagnetic data

Time-scaling properties of ULF geomagnetic signals are analysed by means of the power spectral density, Higuchi method and Hurst R/S analysis. We analyse the three ULF geomagnetic components (two horizontal and one vertical) measured by one station installed in Crete, Greece, one of the most seismically active areas of the Mediterranean Region. The range of time-scales investigated varies from minutes to weeks. It is shown that two time-scaling regimes mainly characterize the temporal fluctuations of the signals. Our results suggest the presence of fractal features expressing long-range time correlation with scaling coefficients, which are the clue of persistent mechanisms.