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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Equator-S observations of drift mirror mode waves in the dawnside magnetosphere
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Equator-S observations of drift mirror mode waves in the dawnside magnetosphere

机译：Equator-S漂移镜像模式波的观测在dawnside磁气圈

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The mirror mode is a plasma instability that is typically excited in high-beta plasmas where there is significant pressure anisotropy and is most commonly observed in the magnetosheath. However, it is possible under sufficiently anisotropic conditions to generate the mirror instability inside the magnetosphere, though as yet there are few examples. We present an extended interval of ～7 hours of mirror mode activity on 19 March 1998 when the Equator-S spacecraft was traversing the dawnside magnetosphere above the equatorial plane at radial distances of up to L ～ 11 and encountered quasi-monochromatic ～2-min oscillations in magnetic field and ion number density, temperature, and velocity. The magnetic field strength and number densities were in antiphase, and the plasma and magnetic field pressure perturbations were also in antiphase while the observed total pressure remained constant. This is consistent with excitation via a mirror instability. We are able to discern that the mirror activity must be confined to approximately within ±20° of the equatorial plane through a conjunction with the Geotail spacecraft. We find that the condition for mirror mode waves to grow is strongly met throughout the interval (Hasegawa, 1969). We believe that this is an excellent high temporal resolution example of the mirror instability exciting ULF waves inside the Earth's magnetosphere. Given the coexistence of toroidal oscillations at almost the same frequency, we suggest coupling between the mirror mode and local standing Alfvén waves. Our observations hence add to the understanding of how energy can be transferred from hot plasma into ULF waves in the magnetosphere before being dissipated in the ionosphere.
机译：镜子模式的等离子体不稳定性在贝塔系数较高的等离子体一般兴奋有显著的各向异性,是压力最常见的观察磁鞘中。然而,它是可能的在充分各向异性条件下生成镜像在磁层不稳定,尽管然而,有一些例子。长间隔的~ 7小时的镜像模式1998年3月19日,当Equator-S活动宇宙飞船是dawnside穿越磁气圈的赤道平面之上径向距离的L ~ 11quasi-monochromatic ~ 2分钟振荡磁场和离子数密度,温度和速度。强度和数量密度在反相,磁场和等离子体的压力扰动也在反相观察到的总压强保持不变。符合激励通过一面镜子吗不稳定。镜子活动必须限于大约在±20°的赤道平面通过一个会同Geotail飞船。镜像模式波的条件强烈见过整个区间吗(长谷川,1969)。优秀的高时间分辨率的例子激动人心的ULF波在镜子不稳定地球的磁气圈。环形振荡几乎相同频率,我们建议镜子之间的耦合模式和地方站阿尔芬波。观察因此增加的理解如何从热等离子能量到ULF波前的磁气圈在电离层消散。

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