Fractal characteristics of the ground-observed ULF emissions in relation to geomagnetic and seismic activities

Results of fractal analysis of ultra-low-frequency (ULF) emissions registered at a low-latitude observatory, Guam (geomagnetic coordinates Φm=9°N, Λm=225°), and at a high-latitude drifting station, North Pole-30 (Φm=75°N, Λm=172°), are presented. The first set of data covers a long period of observations (20 months) including the strong (Ms=8) Guam earthquake of 8 August 1993. The second set of data covers a short period of observations (21 days) in April 1989 during the preparation phase of the big magnetic storm of 25 April 1989. Definite peculiarities in the behavior of ULF emission scaling (fractal) characteristics have been found, which are discussed on the basis of the self-organized criticality concept. The principal common peculiarity for magnetosphere–ionosphere and lithosphere systems is detection of flicker noise (β∼1, D0∼2) in a certain frequency range on the preparation phase of strong magnetospheric and seismic events.