A case study of EMIC wave‐associated He+ energization in the outer magnetosphere: Cluster and Double Star 1 observations
A case study of EMIC wave‐associated He+ energization in the outer magnetosphere: Cluster and Double Star 1 observations
复制标题
DOI：
10.1029/2009ja014784
复制
发表时间：
2010-06
影响因子：
--
通讯作者：
Jichun Zhang;L. Kistler;C. Mouikis;M. Dunlop;B. Klecker;J. Sauvaud
中科院分区：
文献类型：
--
作者：
Jichun Zhang;L. Kistler;C. Mouikis;M. Dunlop;B. Klecker;J. Sauvaud
[1]2004年12月4日，星团飞船上的复合和散射函数（CODIF）分析仪在06：00到10：30 UT观测到一个延长的He+ He事件。在本文中，我们进行了一个案例研究，使用现场等离子体和磁场测量的集群和双星星计划（DSP）谭策1号（TC 1）航天器。在这种情况下，He+离子被激发到1 keV。He+离子加热与三个连续的EMIC波有关，它们发生在黄昏侧磁层侧翼附近，L = 13.1-14.5，这是一个以前没有报道过EMIC波活动的区域。结果，观测到的波频率低至0.03 Hz，远低于典型的EMIC波，即，0.1-5 Hz。结果发现，第一波已经传播了一段时间，并表现出很大的空间范围，而后两个是新产生的各向异性，高能（>1 keV）质子的费用，并有更尖锐的空间边界。与斑片状波活动不同，He+ He区域显示出连续的空间分布，对应于冷离子密度增强的区域。在这个区域中存在各向异性质子和冷密度的原因很可能是安静的地磁条件，这使得质子各向异性发展，等离子体层羽流扩展到如此高的L值。一个差异，发现在比较粒子和波的观测与线性理论，表明该理论应包括他+和/或非线性效应。
[1] On December 4, 2004, the COmposition and DIstribution Function (CODIF) Analyzer on board the Cluster spacecraft observed a prolonged He+ energization event from 06:00 to 10:30 UT. In this paper, we perform a case study of the event by using in situ plasma and magnetic field measurements from the Cluster and Double Star Program (DSP) Tan Ce 1 (TC1) spacecraft. In the event, the He+ ions were energized up to 1 keV. The He+ ion heating was associated with three consecutive EMIC waves, which occurred near the dusk-side magnetospheric flank, L = 13.1–14.5, a region where EMIC wave activity has not been reported before. As a result, the observed wave frequencies, as low as 0.03 Hz, are far lower than those of typical EMIC waves, i.e., 0.1–5 Hz. It is found that the first wave had already propagated for some time and exhibited a large spatial extent, while the latter two were newly generated at the expense of anisotropic, energetic (>1 keV) protons and had sharper spatial boundaries. Unlike the patchy wave activity, the He+ energization region displayed a continuous spatial distribution and corresponded to a region of enhanced cold ion density. The reason for the presence of the anisotropic protons and cold density in this region is most likely the quiet geomagnetic conditions, which allow the proton anisotropy to develop and the plasmaspheric plume to expand into such high L-values. A discrepancy, found in the comparison of particle and wave observations with linear theory, suggests that the theory should include He+ and/or nonlinear effects.