Dynamical Critical Scaling of Space Storms

English Abstract:

Energy dissipation in the terrestrial magnetosphere often follows an intermittent temporal pattern consisting of periods of high activity with sharply increased convection, compressional pulses, intensified fluctuations of field aligned, currents and many other bursty processes, separated by periods of quiescence. Although physical mechanisms of individual activity bursts in the inner magnetosphere have been investigated in numerous studies, in this paper we explore ensemble-averaged statistical properties of these events. We examine statistical properties of bursty multiscale energy dissipation in the inner magnetosphere of Earth based on the dynamics of the SYM‐H index, a global marker of low‐latitude geomagnetic fluctuations. We show that on average, and for time scales shorter than 2 h, temporal development of SYM‐H bursts follows an algebraic form consistent with the predictions from the theory of nonequilibrium phase transitions. The power law exponents describing the probability distributions suggest that the main energy dissipation in the inner magnetosphere takes place because of large activity bursts such as major space storms as opposed to smaller activations whose contribution is less significant despite their much higher relative occurrence. The results obtained provide statistical evidence that the energy dissipation mechanisms associated with magnetospheric activity in the inner magnetosphere are essentially “scale‐free,” displaying dynamical and statistical self‐similarity.