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Ann. Geophys., 24, 3557-3567, 2006
www.ann-geophys.net/24/3557/2006/
© European Geosciences Union 2006
From pre-storm activity to magnetic storms: a transition described in terms of fractal dynamics
G. Balasis1,2, I. A. Daglis1, P. Kapiris1,3, M. Mandea2, D. Vassiliadis4, and K. Eftaxias3
1Institute for Space Applications and Remote Sensing, National Observatory of Athens, Metaxa and Vas. Pavlou St., Penteli, 15236 Athens, Greece
2GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany
3Solid State Section, Physics Department, University of Athens, Panepistimiopolis, Zografos, 15784 Athens, Greece
4NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
Abstract. We show that distinct changes in scaling parameters of the Dst index time
series occur as an intense magnetic storm approaches, revealing a gradual reduction
in complexity. The remarkable acceleration of energy release – manifested in the
increase in susceptibility – couples to the transition from anti-persistent (negative
feedback) to persistent (positive feedback) behavior and indicates that the
occurence of an intense magnetic storm is imminent. The main driver of the Dst
index, the VBSouth electric field component, does not reveal a similar
transition to persistency prior to the storm. This indicates that while the
magnetosphere is mostly driven by the solar wind the critical feature of
persistency in the magnetosphere is the result of a combination of solar
wind and internal magnetospheric activity rather than solar wind variations
alone. Our results suggest that the development of an intense magnetic storm
can be studied in terms of "intermittent criticality" that is of a more
general character than the classical self-organized criticality phenomena,
implying the predictability of the magnetosphere.
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