Geotail observation of cold ion streams in the medium distance magnetotail lobe in the course of a substorm
Geotail observation of cold ion streams in the medium distance magnetotail lobe in the course of a substorm
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DOI：
10.1029/93gl02424
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发表时间：
1994-06
影响因子：
5.2
通讯作者：
T. Mukai;M. Hirahara;S. Machida;Y. Saito;T. Terasawa;A. Nishida
中科院分区：
文献类型：
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作者：
T. Mukai;M. Hirahara;S. Machida;Y. Saito;T. Terasawa;A. Nishida
1992年8月22日，在GEOTAIL卫星上进行的低能粒子（LEP）实验的初始操作中，我们在XGSM <$-42 Re处的磁尾瓣中观测到冷离子束，当时发生了多次亚暴。这些离子束通常由质子和单电荷氧离子（O+）组成，以几乎相同的速度（100-200 km/s）向尾部流动。H+的数密度通常为10−2 cm−3，而O+的密度为10−3 cm−3，但有时会偶尔增加一个数量级。这些离子大概会从向阳面的极地电离层沿着沿着磁力线穿过极地地幔，对流到进行观测的中磁尾。不同种类的离子具有相同的速度，这与E × B对流的速度过滤效应相一致。对它们的速度分布的三维测定揭示了气流方向的偏离黄道角大到几十度。我们讨论了这个功能的增强对流速度，这是与等离子体片变薄局限于一个有限的区域在Y方向。流速的特征变化也被发现与亚暴等离子体团通道。
We observed cold ion beams in the magneto-tail lobe at XGSM ∼ −42 Re in the initial operations of the Low Energy Particle (LEP) experiment onboard the GEOTAIL satellite on August 22, 1992, when multiple onsets of substorms took place. These ion beams generally consisted of protons and singly-charged oxygen ions (O+), flowing tailward with nearly the same velocities ∼ 100–200 km/s. The H+ number density was generally of order 10−2 cm−3, while the O+ density was of order 10−3 cm−3 but at times increased sporadically by an order of magnitude. These ions presumably would be transported along magnetic field lines through the polar mantle from the dayside polar ionosphere and convected to the mid-magnetotail where the observation was made. That different ion species had equal velocities is consistent with the velocity filter effect due to E × B convection. Three-dimensional determinations of their velocity distributions have revealed off-ecliptic angles of the flow directions as large as several tens of degrees. We discuss this feature in terms of the enhanced convection velocity that is associated with the plasma-sheet thinning confined to a limited region in the Y direction. Characteristic changes in the flow velocity are also found in association with a substorm plasmoid passage.