An Analysis of Fractal Dimension of Cosmic Ray Air Shower

Fractal dimensionality of air shower time series data is studied. The fractal dimensions of sequencia! data of air shower time interval are obtained by Takens' method. The fractal dimensionality of 128 time interval data at 19th September 1991 are estimated to be 1.9. This time interval data include the candidate of cluster event of air showers which has 27 events arriving within 2329 sec in contrast to the average rate of 2.4/10 min. The fractal dimension of 128 data in the period just following to the above cluster event on 19th September is estimated to be 2.9. In any other period during which either no candidate of cluster event was found or a candidate of cluster event of less importance was identified by the adaptive cluster method, the chaotic property has not been found until present since June 1991 when the observation of air shower was started by the Air Shower Research Group of Kinki University. Therefore, some of the cluster events of air showers arriving successively seems to be associated with the chaotic property on time series data of air shower interval.