Combined EISCAT radar and optical multispectral and tomographic observations of black aurora
Combined EISCAT radar and optical multispectral and tomographic observations of black aurora
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DOI：
10.1029/2007ja012999
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发表时间：
2008-06-25
影响因子：
2.8
通讯作者：
Blixt, E. M.
中科院分区：
文献类型：
--
作者：
Gustavsson, B.;Kosch, M. J.;Blixt, E. M.
黑色极光被认为是在均匀的漫射极光背景中空间上定义明确的区域，其中光学发射显着减少。黑色极光通常出现在磁午夜后和亚暴恢复阶段，但并不完全如此。我们报告的第一个相结合的多单色光学成像，双基地白光电视记录和非相干散射雷达观测的黑极光的EISCAT的现象。从4278埃的光度比8446埃的光度相对较大的减少，我们表明，非剪切的黑色极光很可能不是由低海拔向下定向的电场引起的。根据观测结果，我们通过将黑色极光的高度和强度与周围背景漫射极光中的沉淀粒子能量相关联来确定这一点。观测结果与能量选择性损失锥更一致。因此，导致黑极光的机制很可能是在磁层中而不是在地球附近活动。
Black auroras are recognized as spatially well-defined regions within a uniform diffuse auroral background where the optical emission is significantly reduced. Black auroras typically appear post-magnetic midnight and during the substorm recovery phase, but not exclusively so. We report on the first combined multimonochromatic optical imaging, bistatic white-light TV recordings and incoherent scatter radar observations of black aurora by EISCAT of the phenomenon. From the relatively larger reduction in luminosity at 4278 angstrom than at 8446 angstrom we show that nonsheared black auroras are most probably not caused by downward directed electrical fields at low altitude. From the observations, we determine this by relating the height and intensity of the black aurora to precipitating particle energy within the surrounding background diffuse aurora. The observations are more consistent with an energy selective loss cone. Hence the mechanism causing black aurora is most probably active in the magnetosphere rather than close to Earth.