Low frequency 1/f-like fluctuations of the AE-index as a possible manifestation of self-organized criticality in the magnetosphere

Low frequency stochastic variations of the geomagnetic AE-index characteriz ed by 1/f(b)-like power spectrum (where f is a frequency) are studied. Base d on the analysis of experimental data we show that the B-z-component of IM F, velocity of solar wind plasma, and the coupling function of Akasofu are insufficient factors to explain these behaviors of the AE-index together wi th the 1/f(b) fluctuations of geomagnetic intensity. The effect of self-org anized criticality (SOC) is proposed as an internal mechanism to generate 1 /f(b) fluctuations in the magnetosphere. It is suggested that localized spa tially current instabilities, developing in the magnetospheric tail at the initial substorm phase can be considered as SOC avalanches or dynamic clust ers, superposition of which leads to the 1/f(b) fluctuations of macroscopic characteristics in the system. Using the sandpile model of SOC, we underta ke numerical modeling of space-localized and global disturbances of magneto spheric current layer. Qualitative conformity between the disturbed dynamic s of self-organized critical state of the model and the main phases of real magnetospheric substorm development is demonstrated. It is also shown that power spectrum of sandpile model fluctuations controlled by real solar win d parameters reproduces all distinctive spectral features of the AE fluctua tions.