Using the R/ S statistic to analyze AE data

Abstract

Recently, it has been proposed that the dynamics of the global geomagnetic current system are consistent with a self-organized critical (SOC) state. Based on that idea, sandpile models of the auroral electrojet index AE have been constructed and compared with data. The Hurst R/ S statistic is a powerful test for the presence of SOC, which is applied to AE time series. Those results are compared with the results of the R/ S statistic for both the solar wind time series ( B z , v sw, etc.) and auroral oval magnetometer time series. We find that the solar wind acts as if it was in a SOC state, and that the AE index time series indicates that AE is in a nearly identical SOC state. We cannot rule out the possibility that the AE results, which are the response to the solar wind, are a reflection of the solar wind SOC state. However, the local measures (ground station magnetometer readings; ground station dynamical signals) give evidence of a different type of SOC state within the magnetosphere.