Changes in fractal properties of geomagnetic indexes as possible magnetic storms precursors

Abstract

Records of Dst, Kp and Sym-H indexes are analyzed looking for evidences of possible precursors for magnetic storms. To accomplish this task the main magnetic storms were located and some periods immediately before storms and some periods well before them studied. Statistical properties of both types of periods were then compared. In particular, were compared the slopes of the power laws that have been found for the distributions of indexes values. A systematic deviation was found between both distributions for the Kp index. It was no so for Dst and Sym-H indexes. For the three indexes it was found a correlation between slopes and the corresponding storm intensity, which could serve as a probabilistic approach to magnetic storms forecasting. The data for the analysis was obtained at the World Data Centre for Geomagnetism at Kyoto.