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-Org anized Critical (SOC) system. To do this we compare the burst lifetime dist ributions of the AU and \AL\ indices with those of the nu B-s and epsilon s olar 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 expo nential cut-off, consistent with the solar wind being an SOC system. Furthe rmore, the power law of the epsilon burst lifetime distribution is not sign ificantly different to that of the AU and \AL\ indices, indicating that thi s scale-free property of the AE indices could arise from the solar wind inp ut and may not be an intrinsic property of the magnetospheric system. We di scuss the implications of this result for SOC theories of the magnetosphere .