Magnetotail response to corotating interaction region driven geomagnetic storms: Cluster observations

Abstract. In this work we have selected 40 corotating/stream interaction (CIR) driven geomagnetic storms that occurred between 2001 and 2016, and statistically studied their impacts on the magnetotail. The wavelet transform was applied to the interplanetary magnetic field (IMF) Bz component, magnetotail Bx component, and the auroral electrojet (AE) index during geomagnetic storms. The cross-wavelet technique was applied to determine the periods of higher correlation between the IMF Bz× magnetotail Bx, IMF Bz×AE index and magnetotail Bx×AE index. More than 80 % of the most energetic periods in the IMF Bz and magnetotail Bx are found to be shorter than 4 h, independently of the storm phase. The AE index presented the range between 2–4 h as the most common with energetic periods for both storm main and recovery phases. In the recovery phase, periodicities in the AE index are more spread (≤12 h) than for the main phase (≤8 h) probably due to the presence of high-intensity long-duration continuous AE activities (HILDCAAs). From the cross-wavelet analysis (IMF Bz× magnetotail Bx, IMF Bz×AE index and magnetotail Bx× AE index), periods≤4 h are found to be dominant in both storm phases, which coincide with the cyclic substorm periods. The power spectral analysis showed that the IMF Bz and magnetotail Bx time series follow the Kolmogorov (-5/3) power law. Additionally, the mean values of the spectral indices for the magnetotail Bx and AE index are higher during the recovery phase than the main phase.This suggests that turbulence is more pronounced during the recovery phase of geomagnetic storms driven by CIRs.