Power law probability distributions of multiscale auroral dynamics from ground-based TV observations

Some of the most significant observational indications of self‐organized critical (SOC) behavior in the magnetosphere are the scale‐free statistical distributions of nighttime auroral emission regions as depicted by the Ultraviolet Imager (UVI) onboard the POLAR spacecraft [Uritsky et al., 2002]. Here, we report the results from a similar study of ground‐based optical observations. Individual active auroral regions have been detected and analyzed using a spatiotemporal technique and statistical methods appropriate for quantifying critical behavior in SOC models. Probability distributions of the lifetime, maximum and integrated size, maximum power, and integrated energy output for auroral emission regions are shown to follow power law relations over wide ranges of scales. The power‐law exponents that we obtained are consistent with the UVI image exponents, extending the range of observed scale‐free auroral SOC dynamics by several orders of magnitude to smaller spatial and temporal scales.