PFISR nightside observations of naturally enhanced ion acoustic lines, and their relation to boundary auroral features
PFISR nightside observations of naturally enhanced ion acoustic lines, and their relation to boundary auroral features
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PFISR 自然增强离子声线的夜间观测及其与边界极光特征的关系
DOI：
10.5194/angeo-26-3623-2008
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发表时间：
2008
影响因子：
1.9
通讯作者：
H. Stenbaek
中科院分区：
文献类型：
--
作者：
R. Michell;K. Lynch;C. Heinselman;H. Stenbaek
我们目前的结果，从协调相机和雷达研究的极光电离层在2006年3月从扑克坪，阿拉斯加。该活动的进行是为了配合扑克牌平板非相干散射雷达（PFISR）第一季度安装的工程测试。2006年3月31日，一个中等强度的极光弧（在557.7 nm处约10 kR）位于扑克平原的磁天顶。在这次事件中，雷达观测到7个不同时期的F区异常大的后向散射功率。这些仅在场对准雷达波束中观察到，这七次的雷达光谱显示自然增强的离子声学线（NEIAL），这是PFISR首次观察到的。这些时间对应于（a）极光椭圆的极帽边界穿过磁天顶时，以及（B）在磁天顶可见小规模的附属暗结构时。（a）和（B）两者的存在是它们发生的必要条件。软电子沉淀发生在磁天顶附近在这些相同的时间。在NEIAL附近的电子密度大约在5到30×10 10 m −3之间。卫星和探空火箭在现场观测到，在活跃的极光条件下，与极光和软电子沉降的极向边缘有关的宽带极低频波活动以类似的形态发生。这里提出的意见建议进一步调查的想法，NEIALs和BBELF波活动是不同的观察方面相同的波现象。如果NEIAL和BBELF之间的联系可以用更多的数据建立起来，这可以提供下行电流区域（DCR）和动态极光的现场测量与暗极光结构和NEIAL的地面观测之间的联系。在地基特征中识别原地过程，即波活动，可能会产生许多影响。感兴趣的一个具体例子是使用地面光学观测在大的空间和时间尺度上识别和跟踪潜在离子流出区域的时间和空间演变。
We present results from a coordinated camera and radar study of the auroral ionosphere conducted during March of 2006 from Poker Flat, Alaska. The campaign was conducted to coincide with engineering tests of the first quarter installation of the Poker Flat Incoherent Scatter Radar (PFISR). On 31 March 2006, a moderately intense auroral arc, (~10 kR at 557.7 nm), was located in the local magnetic zenith at Poker Flat. During this event the radar observed 7 distinct periods of abnormally large backscattered power from the F-region. These were only observed in the field-aligned radar beam, and radar spectra from these seven times show naturally enhanced ion-acoustic lines (NEIALs), the first observed with PFISR. These times corresponded to (a) when the polar cap boundary of the auroral oval passed through the magnetic zenith, and (b) when small-scale filamentary dark structures were visible in the magnetic zenith. The presence of both (a) and (b) was necessary for their occurrence. Soft electron precipitation occurs near the magnetic zenith during these same times. The electron density in the vicinity where NEIALs have been observed by previous studies is roughly between 5 and 30×10 10 m −3 . Broad-band extremely low frequency (BBELF) wave activity is observed in situ by satellites and sounding rockets to occur with similar morphology, during active auroral conditions, associated with the poleward edge of the aurora and soft electron precipitation. The observations presented here suggest further investigation of the idea that NEIALs and BBELF wave activity are differently-observed aspects of the same wave phenomenon. If a connection between NEIALs and BBELF can be established with more data, this could provide a link between in situ measurements of downward current regions (DCRs) and dynamic aurora, and ground-based observations of dark auroral structures and NEIALs. Identification of in situ processes, namely wave activity, in ground-based signatures could have many implications. One specific example of interest is identifying and following the temporal and spatial evolution of regions of potential ion outflow over large spatial and temporal scales using ground-based optical observations.