Fractal character of G index of IPS data for the period 1991–1994, obtained from multiscale wavelet analysis

In the study of the impact of solar activity on the terrestrial magnetosphere, the interplanetary medium plays a major role. Interplanetary scintillation (IPS) is a powerful tool that can be used to study the three-dimensional structure of the heliosphere and to monitor the presence of large scale perturbations in the interplanetary medium originating at the Sun, such as coronal mass ejections. In this paper, the scintillation values, g, that were taken for several years at the dipole array of Cambridge (UK) to make daily sky maps were used to calculate another index, G, which we assume to represent the density structure of the inner heliosphere. We performed wavelet and power spectrum analyses to obtain the local correlations of fluctuations at different scales of the daily G index, for the period 1991–1994. We found evidence of self-organization in the data and thus propose that the interplanetary medium is close to a critical state, at least for certain periods, and that this may explain the noncyclic components of solar activity.