太阳风动压脉冲结构与地磁急始关系研究

Relationship between Dynamic Pressure Pulse and Geomagnetic Sudden Commencement

针对1994-2011年的363例地磁急始事件,基于太阳风动压脉冲(DPP)结构自动识别算法确定是否有相应的太阳风动压脉冲结构事件与其相关联,进而针对太阳风动压脉冲结构地磁急始关联事件进行统计分析研究.研究结果显示:91%的地磁急始事件与DPP事件相关联,53%的地磁急始事件与行星际激波相关联,这表明太阳风动压脉冲结构是引起地磁急始更普遍的原因;引起地磁急始的太阳风动压脉冲结构事件约70%发生在行星际日冕物质抛射、共转相互作用区以及行星际日冕物质抛射和/或共转相互作用区相互作用形成的复杂抛射物等大尺度太阳风扰动结构中,且其平均动压变化幅度为3.9 nPa,强太阳风动压脉冲结构事件占全体事件的42%;地磁急始事件变化幅度与太阳风动压脉冲变化幅度以及上下游动压平方根差之间存在明显的相关关系,相关系数分别为0.79和0.82,并且行星际磁场南向时相关性更强;太阳风动压脉冲结构事件持续时间、传播速度、动压变化幅度对地磁急始事件的持续时间有一定影响,但这些参数与地磁急始事件的相关关系较弱.研究结果可为基于太阳风动压脉冲结构特征参数开展地磁急始预报提供研究基础.

A deep understanding of the relationship between geomagnetic SC （Sudden Commence- ment） and DPP （Dynamic Pressure Pulse） is important for comprehensively understanding the re- sponse characteristics of geomagnetic field to interplanetary disturbance and improving the ability of SC prediction. In this paper, 363 SC events observed between 1994 and 2011 are the objectives. Firstly, whether there are corresponding DPP events associated with the SC events or not are de- termined by using automatic DPP recognition algorithm. Secondly, the characteristics of the DPP events and the SC events as well as their relationship statistically are analyzed. The results are as follows. 91% of the SC events are associated with the DPP events, and 53% of the SC events are associated with the shocks. The DPP events and the shocks are observed by WIND satellite. Thisresult indicates that DPP is the main cause of SC. Most of the DPP events （70%） that cause the SC events are associated with large scale solar wind structures, such as Interplanetary Coronal Mass Ejections （ICME）, Corotating Interaction Region （CIR） and complex projections aused by ICME and/or CIR. And the averaged dynamic pressure amplitude change of the DPP events is 3.9 nPa. Strong DPP events account for 42% of all the events. There is an obvious relationship between the amplitude of the SC events and the absolute dynamic pressure change as well as the difference of the square root of the dynamic pressure of the DPP events, and the correlation coefficients are 0.79 and 0.82, respectively. The correlations between them are much stronger when the interplanetary magnetic field is southward. Although the duration, speed and amplitude of DPP have a certain influence on the duration of SC respectively, there is no obvious relationship between them. These results contribute to the prediction of SC based on DPP parameters.