A statistical analysis of solar wind parameters and geomagnetic indices for the Solar Cycle 23
SHEN Xiao-Fei;NI Bin-Bin;GU Xu-Dong;ZHOU Chen;LIU Yong;XIANG Zheng;ZHAO Zheng-Yu;School of Physical Science and Technology,Wuhan University;Department of Space Physics,School of Electronic Information,Wuhan University;State Key Laboratory of Space Weather,Chinese Academy of Sciences;
Coronal mass ejections(CMEs)and corotating interaction regions(CIRs)are two significant contributors to interplanetary disturbances and geomagnetic disturbances,which also play as major drivers of geomagnetic storms to modulate the geo-space environment.In order to comprehensively investigate the characteristic temporal features of the solar wind activity and associated geomagnetic activity,a large amount of solar wind data and geomagnetic activity indices are analyzed in detail.Firstly,using the public data of solar wind parameters and geomagnetic activity indices provided by the NASA OMNIWeb,the MATLAB codes are developed to deal with a number of key parameters including IMF Bz,solar wind velocity,solar wind proton density,solar wind dynamic pressure,Dst,AE,and Kpfor the entire Solar Cycle23 from 1996to 2008.The complete database with a full list of 269 CME events and 456 CIR events is identified.Case event studies and superposed epoch analyses are implemented to carefully investigate the statistical features of four important solar wind parameters(IMF Bz,solar wind speed,solar wind proton density,and solar wind dynamic pressure)and three major geomagnetic indices(Dst,AE,and Kp)associated with the two types of solar disturbances.Secondly,the minimum of Dst index is utilized to differentiate 355 isolated geomagnetic storms occurring during the Solar Cycle 23.These storms are further categorized according to the magnitude of Dst minimum into 145 weak storms,123 moderate storms,70 strong storms,12 severe storms,and 5extreme storms.Finally,superposed epoch analysis is applied to evaluate the statistics of solar wind parameters and geomagnetic indices corresponding to magnetic storms with different intensities.It is found that in general the linearly fitted slope of Nsw/Pdyn(where Nswis the solar wind proton density and Pdynthe 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 Kpindices 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.There are a large number of differences between CME and CIR events and their driven geomagnetic storms as well.Therefore,CME-driven storms and CIR-driven storms should be studied separately.The established database of CME and CIR events and geomagnetic storms and the quantitative statistical information in combination can provide a useful aid for better understanding the responses of Earth′s plasma sheet,radiation belts,and ring current to various solar activities.
【Fund】： 国家自然科学基金(41204120 41304130 41474141);; 中央高校自主科研项目(2042014kf0251 2042014kf0269);; 中国博士后科学基金(2013M542051)联合资助
【CateGory Index】： P353
【CateGory Index】： P353