Spatial scaling of optical fluctuations during substorm-time aurora

Abstract

A study of statistical features of auroras during substorm activity is presented, emphasizing characteristics which are commonly applied to turbulent flows. Data from all-sky television (TV) observations from the Barentsburg observatory (Svalbard) have been used. Features of the probability density function (PDF) of auroral fluctuations have been examined at different spatial scales. We find that the observed PDFs generally have a non-Gaussian, heavy-tailed shape. The generalized structure function (GSF) for the auroral luminosity fluctuations has been analyzed to determine the scaling properties of the higher (up to 6) order moments, and the evolution of the scaling indices during the actual substorm event has been determined. The scaling features obtained can be interpreted as signatures of turbulent motion of the magnetosphere-ionosphere plasma. Relations to previously obtained results of avalanche analysis of the same event, as well as possible implications for the validity of self-organized criticality models and turbulence models of the substorm activity, are discussed.