行星际电场与Dst指数

CORRELATIONS OF Dst INDEX WITH THE INTERPLANETARY ELECTRIC FIELD

利用ＡＣＥ卫星的太阳风及行星际磁场观测数据和相应时期的Ｄｓｔ指数，分析了行星际电场和Ｄｓｔ指数的相关关系，讨论了行星际电场作为研究磁层和太阳风相互作用的良好参数的物理机制．结果表明：行星际电场与Ｄｓｔ指数有很好的相关性，并且在强和中等地磁活动期间，存在显著的突变特征曲线；相对于丁、Ｖ２Ｂｚ、ＶＢ２和ε，行星际电场的突变特征曲线更易识别；弱的扰动磁层背景状况和行星际磁场南向分量及电场晨昏分量的较大波动影响着磁暴的发展，使磁暴主相有多个发展阶段，从而增加磁暴的强度；对主相有多个发展阶段磁暴的研究有待进一步改善．

Correlations of the Dst index with various interplanetary parameters are stud ied by using the solar wind and interplanetary magnetic field data from the ACE spacecraft. Among all parameters investigated, Ey, the down-dusk component of the interplanetary electric field is found to be best correlated with the Dst index. During strong and moderate geomagnetic storms, it is seen that 2 to 3 hours before the storm main phase starts, Ey suddenly begins to increase and that the increase of Ey, is almost 'synchronous' with the decrease of the Dst, with a time a head about 2 to 3 hours. Such an 'abruptly changing characteristic curve' of Ey is much easier to be identified than those corresponding curves of V , V2Bz .. VB2 and ε. Weak disturbances in the magnetospheric background field, fluctuations of both the IMF Bz and the interplanetary Ey all strongly influence the development of storms, causing multiple-step main phase decrease and enhancement of the storm intensity. The physical mechanism responsible for the close correlation of Dst with the interplanetary electric field is discussed. A viewpoint that the present study of multiple-step main phase storms needs to be improved is proposed.