Multispacecraft observations of sudden impulses in the magnetotail caused by solar wind pressure discontinuities: Wind and IMP 8
Multispacecraft observations of sudden impulses in the magnetotail caused by solar wind pressure discontinuities: Wind and IMP 8
复制标题
DOI：
10.1029/97ja02870
复制
发表时间：
1998-08
影响因子：
--
通讯作者：
M. Collier;J. Slavin;R. Lepping;K. Ogilvie;A. Szabo;H. Laakso;S. Taguchi
中科院分区：
文献类型：
--
作者：
M. Collier;J. Slavin;R. Lepping;K. Ogilvie;A. Szabo;H. Laakso;S. Taguchi
与风暴突然开始相关的两个上游太阳风压力不连续性已经被检查，以确定它们对地磁尾瓣场的影响。在1995年3月9日和1995年8月17日发生的两次事件中，Wind航天器位于上游区域监测太阳风，IMP 8航天器位于地磁尾瓣观察尾部响应。这两次事件发生在行星际磁场向北或向南较弱的时期。在每种情况下，数据表明尾瓣中的磁场强度直接响应外部太阳风压力的增加而增加。结果表明，通过阶跃函数收缩压缩均匀磁场的简单模型可以准确预测几分钟数量级的特征时间尺度和磁场分布。推断的展开角与模型预测一致，并且不连续性上的展开角的变化对应于基于太阳下磁层顶位置和尾部宽度变化的预期。总体而言，这项研究的结果表明，即使磁尾对行星际压力不连续性做出快速响应，也能保持近似的 MHD 平衡。
Two upstream solar wind pressure discontinuities that were associated with storm sudden commencements have been examined to determine their effect on the geomagnetic tail lobe field. During the two events, occurring on March 9, 1995, and August 17, 1995, the Wind spacecraft was located in the upstream region monitoring the solar wind, and the IMP 8 spacecraft was in the geomagnetic tail lobe observing the tail response. The two events occurred during periods with northward or weak southward interplanetary magnetic field. In each case, the data suggest that the magnetic field in the tail lobe increased in magnitude directly in response to the external solar wind pressure increase. It is shown that a simple model in which a uniform magnetic field is compressed by a step function constriction accurately predicts characteristic timescales, which are of the order of a couple minutes, and the magnetic field profiles. The inferred flaring angles are consistent with model predictions, and the changes in the flaring angle across the discontinuities correspond to expectations based on changes in the subsolar magnetopause position and tail width. Overall, the results of this study indicate that the magnetotail maintains an approximate MHD equilibrium even as it responds rapidly to interplanetary pressure discontinuities.