Fractal structure of cosmic ray intensity variations

Time series of cosmic ray (CR) intensity recorded at a low cut-off rigidity neutron monitor, Calgary (CA), are checked for scaling properties. Three years of 5-min data from CA and ten days of 10-sec measurements at Lomnický stit (LS) are analyzed. Power spectrum analysis, and two methods of checking fractality, namely the yardstick length method and the method of scaling exponent, are applied to the 2 14 data points. As compared to CRs at higher energies, the examined data have a more complicated scaling structure, affected by disturbances in the heliosphere. Regions, where fractal description is appropriate, are 30 – 300 hours and 40 min – 8 hours. While the 40-minute limit is probably the signature of a vanishing effect of interplanetary magnetic field (IMF) on CRs, the other limits are due to diurnal and 27 day variations. Scaling of the higher moments of CR time series involves the signature of multifractality. However, the present statistical significance is not sufficient for a detailed investigation of this problem.