Comparative study of dynamical critical scaling in the auroral electrojet index versus solar wind fluctuations

Based on an analysis of auroral electrojet (AE) index data, we demonstrate that the temporal evolution of magnetospheric perturbations exhibits non-tr ivial power-law relations consistent with the behavior of a general class o f statistical physical models in the vicinity of a stationary critical poin t. We show that the ensemble average dynamics of the activity bursts in the AE index is essentially scale-free and can be characterized in terms of sp reading critical exponents eta and delta. The lifetime T and the size S of the bursts show strong algebraic correlation that is approximated by the de pendence S similar to T1+eta+delta. For times shorter than 3.5 hours, we fi nd scaling features in the AE index that are independent of the solar wind input, thus indicating the internal magnetospheric origin of the revealed e ffects.