On-off Intermittence as a Possible Mechanism of Geomagnetic Impulse Generation

Abstract

Using the many-year observations at several high-latitude observatories in the Northern and Southern Hemispheres, the regularities in distribution of magnetic impulse events (MIEs) amplitudes are studied. It is shown that the tails of the functions of statistical distributions of impulse amplitudes are approximated by a power function of the form f (A) = A**(-b), where A is the impulse amplitude, and b is the power index laying in the range from 1 to 5. Experimental confirmation is obtained to the hypothesis suggested earlier that the impulse generation regime qualitatively corresponds to the model of on-off intermittency. It is assumed that the model of the on-off intermittency may be considered as one of the possible mechanisms of MIEs generation. It is found that the majority of the analyzed statistical distributions of MIEs amplitudes have the index b exceeding 2, the fact being typical for chaotic regimes called the strong turbulence. In some cases the index b is close to the unity, this fact being typical for the regimes generated in weakly turbulized medium. The results obtained make it possible to assume that: a) at higher magnetospheric latitudes, the plasma turbulence degree is higher that at lower latitudes, b) in the afternoon sector of the magnetosphere, the plasma is stronger turbulized than in the prenoon sector; c) in the Northern and Southern Hemispheres the magnetospheric plasma is stronger turbulized in summer and winter, respectively; d) at the growth phase of solar activity the magnetospheric plasma is stronger turbulized than at the declining phase. The dependence of the power index b on the solar wind parameters and IMF demonstrates the influence of interplanetary conditions on the high-latitude magnetosphere plasma where MIEs are formed.