Statistical altitude distribution of the auroral density cavity
Statistical altitude distribution of the auroral density cavity
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DOI：
10.1002/2014ja020691
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发表时间：
2015-02-01
影响因子：
2.8
通讯作者：
Karlsson, T.
中科院分区：
文献类型：
--
作者：
Alm, L.;Li, B.;Karlsson, T.
利用极光加速通量管的现场观测，研究了位于3.0-6.5R-E之间的极光密度空洞的统计高度分布。观测的位置是用从卫星上方和下方的平行势降分布得出的伪高度来描述的。极光加速区的上缘位于4.375-5.625 R-E之间。在6.125 R-E以上，虽然可以观察到向上的离子束，但没有一个事件显示出沉淀的倒置V电子。这表明卫星位于与极光加速区相同的通量管内，但在极光加速区之上。电子密度随着我们进入加速区的高度而降低。一旦超过加速区，航天器势能继续降低，这表明密度空穴延伸到加速区以上。从3.0R-E到4.375 R-E，伪高度每R-E增加0.2个，与分布的平行电场一致。在4.375-5.625 R-E之间，由于发生在加速区上方的每个高度槽的事件数量增加，伪高度微弱增加，每R-E增加0.01%。在5.625 R-E以上，由于加速区上方每个高度面元的事件数迅速增加，每R-E的拟高度增加0.28个，这表明剩余的平行电势降集中在加速区上缘的狭窄区域，而不是分布在平行电场中。
The statistical altitude distribution of auroral density cavities located between 3.0 and 6.5 R-E is investigated using in situ observations from flux tubes exhibiting auroral acceleration. The locations of the observations are described using a pseudo altitude derived from the distribution of the parallel potential drop above and below the satellite. The upper edge of the auroral acceleration region is observed between 4.375 and 5.625 R-E. Above 6.125 R-E, none of the events exhibit precipitating inverted V electrons, though the upward ion beam can be observed. This indicates that the satellites are located inside the same flux tube as, but above, the auroral acceleration region. The electron density decreases as we move higher into the acceleration region. The spacecraft potential continues to decrease once above the acceleration region, indicating that the density cavity extends above the acceleration region. From 3.0 to 4.375 R-E the pseudo altitude increases by 0.20 per R-E, consistent with a distributed parallel electric field. Between 4.375 and 5.625 R-E the pseudo altitude increases weakly, by 0.01 per R-E, due to an increasing number of events per altitude bin, which are occurring above the acceleration region. Above 5.625 R-E the pseudo altitude increases by 0.28 per R-E, due to a rapid increase in the number of events per altitude bin occurring above the acceleration region, indicating that the remaining parallel potential drop is concentrated in a narrow region at the upper edge of the acceleration region, rather than in a distributed parallel electric field.