Midnight sector observations of auroral omega bands MIDNIGHT SECTOR AURORAL OMEGA BANDS
Midnight sector observations of auroral omega bands MIDNIGHT SECTOR AURORAL OMEGA BANDS
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午夜扇区极光欧米茄带观测 午夜扇区极光欧米茄带
DOI：
10.1029/2010ja015874
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Wild J
中科院分区：
文献类型：
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作者：
Wild J
我们在2009年9月28日对极光欧米茄波段进行了观测。虽然一般与亚暴恢复阶段，通常在上午部门观察到，这里提出的功能发生后不久，扩张阶段的发病和观察到的午夜部门，黎明的发病地区。位于冰岛东北部的全天空成像仪显示，欧米茄带的大小为150 × 200 km，并以10.4 km s-1的速度向东传播，而一个位于同一地点的地面磁力计记录了Ps 6脉动的同时发生。虽然比之前报道的大多数欧米茄带要小一些，移动也慢一些，但观测到的结构是这种现象的明显例子，尽管是在一个非典型的位置，而且在亚暴周期的早期。THEMIS C探测器提供了上游行星际环境的详细测量，而星团卫星位于与地面全天空成像仪共轭的尾部等离子体片中。星团的卫星观测到0.1-3 keV电子的爆发，这些电子平行于磁场向北方半球极光电离层移动;这些爆发与场向坡印廷通量的增加有关。在现场测量是一致的电子加速通过剪切阿尔文波在等离子体片108 REtailward的地球。虽然没有发现极光和磁层特征之间的一对一关联，但我们的观测表明，等离子体片中的阿尔文波是导致电离层中Ps 6脉动和极光增亮的场向电流的原因。我们的研究结果与早期研究的结论一致，即极光欧米茄带在中尾等离子体片中有一个源机制。
We present observations of auroral omega bands on 28 September 2009. Although generally associated with the substorm recovery phase and typically observed in the morning sector, the features presented here occurred just after expansion phase onset and were observed in the midnight sector, dawnward of the onset region. An all‐sky imager located in northeastern Iceland revealed that the omega bands were ∼150 × 200 km in size and propagated eastward at ∼0.4 km s−1while a colocated ground magnetometer recorded the simultaneous occurrence of Ps6 pulsations. Although somewhat smaller and slower moving than the majority of previously reported omega bands, the observed structures are clear examples of this phenomenon, albeit in an atypical location and unusually early in the substorm cycle. The THEMIS C probe provided detailed measurements of the upstream interplanetary environment, while the Cluster satellites were located in the tail plasma sheet conjugate to the ground‐based all‐sky imager. The Cluster satellites observed bursts of 0.1–3 keV electrons moving parallel to the magnetic field toward the Northern Hemisphere auroral ionosphere; these bursts were associated with increased levels of field‐aligned Poynting flux. The in situ measurements are consistent with electron acceleration via shear Alfvén waves in the plasma sheet ∼8REtailward of the Earth. Although a one‐to‐one association between auroral and magnetospheric features was not found, our observations suggest that Alfvén waves in the plasma sheet are responsible for field‐aligned currents that cause Ps6 pulsations and auroral brightening in the ionosphere. Our findings agree with the conclusions of earlier studies that auroral omega bands have a source mechanism in the midtail plasma sheet.