Abstract
The correlation dimension d GP of cosmic ray muon time series recorded at Misato underground station at a depth of 34 hg/cm 2 has been calculated by means of the Grassberger and Procaccia algorithm. From the time series, background white noise which is caused by the counting-rate error and gives a serious impact on the estimation of d GP is removed by means of a technique of the wavelet expansion. Marked periodic variations which are caused by cosmic ray anisotropies and make it difficult to obtain a reliable value of d GP are also removed from the time series by means of a recursive digital filter. Using the muon time series which is apparently free from both the background white noise and the daily variation, we could estimate a reliable value of the correlation dimension for three different periods which correspond to different levels of solar activity. It is found that the correlation dimension changes only slightly with the level of solar activity.
Published Version
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