A Statistical Analysis of Solar Wind Parameters and Geomagnetic Indices during the Solar Cycle 23

AbstractInterplanetary Coronal mass ejections (CMEs) and corotating interaction regions (CIRs) are two types of most geoeffective solar wind transients and also the main drivers of geomagnetic storms. In this study, by using a superposed epoch analysis, we have compared the statistical features of solar wind parameters for the two types of solar disturbances during the 23rd solar cycle and the resulting changes of geomagnetic indices (Dst, AE, and Kp). Meanwhile, the statistics of solar wind parameters and geomagnetic indices corresponding to magnetic storms with different intensities are also investigated. In general, it is found that the slopes of linearly fitted Nsw/Pdyn curves (where Nsw is the solar wind proton density and Pdyn is the solar wind dynamic pressure) with respect to epoch time remains positive for CME events but negative for CIR events, which can act as a feasible means to distinguish CME and CIR events. On average, compared to CIR events, CME events have larger magnitudes of southward IMF Bz, solar wind dynamic pressure, AE and Kp indices but smaller Dstmin. In principle, CMEs bear higher possibility to drive extremely intense (i.e., super) geomagnetic storms. The overall variations of Dst tend to be similar to some extent for different levels of geomagnetic storms, however, Dst decreases faster for stronger storms.