![]() ![]() Therefore, a detailed and comprehensive investigation of the temporal features of the solar wind and the geomagnetic activity is very important to recognize systematically the characteristic responses of Earth’s magnetosphere to solar activity and the solar wind-magnetosphere particle and energy coupling processes. Geomagnetic storms are mainly driven by CMEs and CIRs( Turner et al., 2009), impacting remarkably on the dynamics of magnetospheric particles and the perturbation of various plasma waves( Reeves et al., 2003), on the timescales from seconds to months or more. They occur frequently with Dst above -100 nT without SSCs. CIR-driven storms are of longer duration and weaker intensity. In contrast, CIR events are always moderate, primarily occurring during solar minima. CME-driven storms are of shorter duration and large intensity, commonly with storm sudden commencements(SSCs). CME events are a kind of large-scale solar activity, which mainly occur during solar maxima. CMEs and CIRs are the main factors that influence the geomagnetic activity( Heber et al., 1999 Cane and Richardson, 2003 Zhang et al., 2008). When the geomagnetic environment changes, especially during intense magnetic storms, environments of the ionosphere, upper atmosphere and particle radiation will respond strongly, resulting in severe space weather effects to pose a potential danger to orbiting spacecraft and astronauts in space. Geomagnetic activity is an important phenomenon, largely affected by the solar wind. The coupling also affects both the current systems and spatial regions in the magnetosphere, including the ring current and the radiation belts( Yuan, 2011). The coupling of solar wind and Earth’s magnetosphere triggers currents and electric fields, drives large-scale magnetospheric convections, causes changes of the magnetopause configuration, generates inner changes of the magnetosphere, and finally produces magnetic storms or substorms. When the solar wind encounters the Earth, the geomagnetic field can shield it, and the bow shock, magnetosheath and magnetopause are formed. The solar wind is composed of the plasma flow coming from the Sun and the interplanetary magnetic field flowing with the plasma. Omniweb nasa dst index drivers#Abstract: Interplanetary 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 N sw/ P dyn curves(where N sw is the solar wind proton density and P dyn 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 B z,solar wind dynamic pressure,AE and Kp indices but smaller Dst min.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. ![]()
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