A statistical study of EMIC waves observed by Cluster: 2. Associated plasma conditions
A statistical study of EMIC waves observed by Cluster: 2. Associated plasma conditions
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DOI：
10.1002/2016ja022541
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发表时间：
2016-07-01
影响因子：
2.8
通讯作者：
Jordanova, V. K.
中科院分区：
文献类型：
--
作者：
Allen, R. C.;Zhang, J. -C.;Jordanova, V. K.
这是两篇论文中的第二篇，讨论了在10年（2001-2010）的星团观测中检测到的电磁离子回旋（EMIC）波的统计研究。在第一篇论文中，分析了EMIC波的特性（即，波功率、极化、法线角和波传播角）在磁纬度（MLAT）-距离以及磁地方时（MLT）-L框架中呈现。本文着重于EMIC波相关的等离子体条件的分布，以及两个EMIC波产生代理（电子等离子体频率陀螺频率比代理和线性理论代理）在这些相同的框架。根据热H ~+各向异性分布、电子和热H ~+密度测量、热H ~+平行等离子体β分布以及计算的波产生代理，EMIC波存在三个源区：（1）在午后至黄昏MLT区，冷等离子体层或羽流群与热各向异性环电流群的重叠区;（2）沿向阳面磁层沿着的高L壳层区域与向阳面磁层压缩和漂移壳层分裂有关;（3）离赤道区域可能与向阳面磁层中的Shabansky轨道有关。
This is the second in a pair of papers discussing a statistical study of electromagnetic ion cyclotron (EMIC) waves detected during 10years (2001-2010) of Cluster observations. In the first paper, an analysis of EMIC wave properties (i.e., wave power, polarization, normal angle, and wave propagation angle) is presented in both the magnetic latitude (MLAT)-distance as well as magnetic local time (MLT)-L frames. This paper focuses on the distribution of EMIC wave-associated plasma conditions as well as two EMIC wave generation proxies (the electron plasma frequency to gyrofrequency ratio proxy and the linear theory proxy) in these same frames. Based on the distributions of hot H+ anisotropy, electron and hot H+ density measurements, hot H+ parallel plasma beta, and the calculated wave generation proxies, three source regions of EMIC waves appear to exist: (1) the well-known overlap between cold plasmaspheric or plume populations with hot anisotropic ring current populations in the postnoon to dusk MLT region; (2) regions all along the dayside magnetosphere at high L shells related to dayside magnetospheric compression and drift shell splitting; and (3) off-equator regions possibly associated with the Shabansky orbits in the dayside magnetosphere.