Magnetosheath dynamic pressure enhancements: occurrence and typical properties
Magnetosheath dynamic pressure enhancements: occurrence and typical properties
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DOI：
10.5194/angeo-31-319-2013
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发表时间：
2013-01-01
影响因子：
1.9
通讯作者：
Horbury, T. S.
中科院分区：
文献类型：
--
作者：
Archer, M. O.;Horbury, T. S.
首次对磁鞘动压力的大振幅（bbb100 %）瞬态增强进行的综合统计研究表明，这些事件的持续时间长达3毫米，平均持续时间约为30秒，是环境动压力的15倍，主要发生在准平行冲击的下游。动压瞬态通常是由速度增加和密度的小分数增加所主导的，尽管速度通常只发生几度的偏转。磁场的叠加小波变换表明，虽然大多数增强表现为磁鞘磁场的变化，但大多数与行星际磁场（IMF）的变化无关。然而，有少数的增强似乎与太阳风的不连续性有关，这不能简单地用随机事件来解释。一般来说，发现在磁鞘动压增强期间，IMF比平时更稳定。这表明稳定的前震以及前震结构或过程在大多数磁鞘动态压力增强的产生中可能是重要的。
The first comprehensive statistical study of large-amplitude (> 100 %) transient enhancements of the magnetosheath dynamic pressure reveals events of up to similar to 15 times the ambient dynamic pressure with durations up to 3 mm and an average duration of around 30s, predominantly downstream of the quasi-parallel shock. The dynamic pressure transients are most often dominated by velocity increases along with a small fractional increase in the density, though the velocity is generally only deflected by a few degrees. Superposed wavelet transforms of the magnetic field show that, whilst most enhancements exhibit changes in the magnetosheath magnetic field, the majority are not associated with changes in the Interplanetary Magnetic Field (IMF). However, there is a minority of enhancements that do appear to be associated with solar wind discontinuities which cannot be explained simply by random events. In general, it is found that during periods of magnetosheath dynamic pressure enhancements the IMF is steadier than usual. This suggests that a stable foreshock and hence foreshock structures or processes may be important in the generation of the majority of magnetosheath dynamic pressure enhancements.