Response of the Magnetosphere -ionosphere- earth system to solm Wind Dynamic Prssure Variation

1.本文对1991年3月24日发生的一次地磁暴始进行了详细的分析。结果表明：（1）A（Kakioka为202 nT）短持续时间正H分量脉冲（2）这种脉冲是由于整个磁层突然压缩效应从昼侧向夜侧传播而引起的;（3）产生脉冲的动力压力脉冲必须存在于太阳风中。（4）脉冲在地球附近的传播，脉冲的峰值在电离层中以HM波速度传播，但其开始在电离层和地球之间的空间中几乎瞬时传播，（5）大约6小时后，在全球范围内观测到一次相干的Pc-5地磁脉动.通过对Kakioka观测到的大SC的分析，发现：（1）最大的SC出现在1940年3月24日，振幅为273 nT;（2）在1924 ~ 1994年期间，观测到12个振幅大于100 nT的SC;（3）大振幅的SC往往出现在太阳黑子数的下降阶段. Dst指数与太阳风动压（Pd）的平方根的散点图显示了一个线性增加的上包络线。我们解释说，这个信封显示Pd依赖Dst。4。我们还分析了（1）地面观测到的连续负地磁脉冲，（2）地球同步磁层顶穿越，和（3）1994年2月21日的SC。

1. A geomagnetic sudden commencement (SC) occurred on March 24,1991 was analyzed in detail. It was found that (1) A large (202nT at Kakioka) positive H-component pulse of short duration (about 1 min) appeared in the initial stage of SC.Such a sharp pulse has never been observed before, (2) This pulse was caused by propagation of the effect of a sudden compression of the whole magnetosphere from dayside to nightside, (3) A sharp pulse of the dynamic pressure should exist in the solar wind in order to produce the pulse, (4) As for the propagation of the pulse near the earth, the peak of the pulse propagated with HM wave velocity in the ionosphere but its onset propagated nearly instantaneously in the space between the ionosphere and the earth, (5) A coherent Pc-5 geomagnetic pulsation was observed world-widely after about 6 hours.2. We analyzed past large SCs observed at Kakioka and found that (1) The largest SC occurred on March 24,1940 and its amplitude was 273nT,(2)Twelve SCs with amplitude larger than 100nT were observed in the period between 1924 and 1994, (3)large amplitude SCs tend to occur in the declining phase of the sunspot number.3. A scatter plot of the Dst index versus the square root of the solar wind dynamic pressure (Pd) shows a upper envelope increasing linearly. We interpret that this envelope shows Pd dependence of Dst.4. We also analyzed (1) successive negative geomagnetic impulses observed on the ground, (2) geosynchronous magnetopause crossings, and (3) SC on February 21,1994.