Multifractal features in short-term time dynamics of ULF geomagnetic field measured in Crete, Greece

A multifractal characterization of the short-term time dynamical fluctuations of the ultra low frequency geomagnetic field, measured by one station installed in Crete, Greece, has been carried out. The three measured components, two horizontal (x and y) and one vertical (z), have shown the presence of four powerful periodicities (24-, 12-, 8- and 6-h periodicities). Using a set of multifractal parameters, defined from the shape of the multifractal spectrum, it has been observed that the degree of multifractality, that characterizes the original signals, is “weaker” if compared to the residual signals, obtained from the original ones after removing the four periodicities. Furthermore the horizontal x-and y-components have revealed to be less multifractal than the vertical z-component.