Evidence for a solar wind origin of the power law burst lifetime distribution of the AE indices

In this paper we examine the claim that the power law distribution of burst lifetimes in the AE index is evidence that the magnetosphere is a Self-Organized Critical (SOC) system. To do this we compare the burst lifetime distributions of the AU and \AL\ indices with those of the nu B-s and epsilon solar wind input functions. We show for the first time that both the nu B-s and epsilon burst lifetime distributions are of power law form with an exponential cut-off, consistent with the solar wind being an SOC system. Furthermore, the power law of the epsilon burst lifetime distribution is not significantly different to that of the AU and \AL\ indices, indicating that this scale-free property of the AE indices could arise from the solar wind input and may not be an intrinsic property of the magnetospheric system. We discuss the implications of this result for SOC theories of the magnetosphere.