Multiple energy‐dispersed ion signatures in the near‐Earth magnetotail: Geotail observation
Multiple energy‐dispersed ion signatures in the near‐Earth magnetotail: Geotail observation
复制标题
近地磁尾中的多个能量色散离子特征：Geotail 观测
DOI：
10.1029/2002gl016637
复制
发表时间：
2003
影响因子：
5.2
通讯作者：
T. Mukai
中科院分区：
文献类型：
--
作者：
Y. Kazama;T. Mukai
Geotail航天器在彗尾下方~ 10 Re和尾侧~ 4 Re的等离子体薄片中观察到多个能量分散离子特征，对应于极地/紫外线记录的小而局部的极光增强。它们还伴随着磁场的双极化和电子平行压力的增强。所有分散的特征都被解释为由于在与观测点磁连接的偏远地区产生的离子团的飞行时间效应。它们可以根据能量和俯仰角分为两种类型。一种是在相空间中具有新月形分布和在磁场方向上具有逆流的高能分量。另一种能量从2 keV分散到60 eV，是沿磁力线单向流出地球的准直光束。前者被解释为在中尾区域产生的弹跳离子簇，其过程与对流激波模型相似，而后者最有可能是来自电离层的质子向上流动。磁层-电离层耦合的一个有趣点是，沿同一场管在中尾区和电离层上方几乎同时发生离子加速。
Multiple energy‐dispersed ion signatures were observed by the Geotail spacecraft in the plasma sheet at ∼10 Re down the tail and ∼4 Re on the duskside, corresponding to a small and localized auroral intensification recorded by Polar/UVI. They were also accompanied by magnetic field dipolarization and enhancement of electron parallel pressure. All the dispersed signatures are interpreted as due to a time‐of‐flight effect of ion clusters produced in remote regions magnetically connected to the observation site. They can be categorized into two types in terms of energies and pitch angles. One is the higher‐energy components having crescent‐shaped distributions in the phase space and counterstreaming in the magnetic field direction. The other, of which the energy was dispersed from 2 keV down to 60 eV, was a collimated beam along the magnetic field line and unidirectionally streaming away from the Earth. The former is interpreted as bouncing ion clusters which are produced in a mid‐tail region with a similar process to the convection surge model, while the latter is most likely to be protons upflowing from the ionosphere. An interesting point in terms of the magnetosphere‐ionosphere coupling is nearly the simultaneous occurrence of ion accelerations in the mid‐tail region and above the ionosphere along the same field tube.