On the spatial distribution of decameter‒scale subauroral ionospheric irregularities observed by SuperDARN radars
On the spatial distribution of decameter‒scale subauroral ionospheric irregularities observed by SuperDARN radars
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DOI：
10.1002/jgra.50475
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发表时间：
2013-08
期刊：
影响因子：
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通讯作者：
S. D. Larquier;P. Ponomarenko;A. J. Ribeiro;J. Ruohoniemi;J. Baker;K. Sterne;M. Lester
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文献类型：
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作者：
S. D. Larquier;P. Ponomarenko;A. J. Ribeiro;J. Ruohoniemi;J. Baker;K. Sterne;M. Lester
在安静地磁条件下，中纬度超级双极光雷达网（SuperDARN）雷达定期从十米尺度电离层密度不规则中观测夜间低速亚极光电离层散射（SAIS）。为了确定导致低速SAIS的密度不规则性的来源，有必要区分高频（HF）传播和不规则性本身对观测到的后向散射分布的影响。我们将黑石超级雷达的距离、方位角和高程数据与假设均匀不规则分布的国际参考电离层的射线追踪建模结果进行了比较。观测到的分布和模拟的分布非常相似。后向散射的空间分布符合高频射线传播时与地磁力线近似垂直（纵横角≤1°）的要求。这是第一次确定造成低速SAIS的不规则性延伸到200至300公里高度之间，验证了先前低速SAIS是f区现象的假设。我们发现，这类电离层后向散射在超级雷达视场中的有限空间范围是高频传播效应和散射不规则性的有限垂直范围的结果。我们的结论是，导致低速SAIS的密度不规则性在中纬度电离层内广泛分布，但仅限于底部f区。
The midlatitude Super Dual Auroral Radar Network (SuperDARN) radars regularly observe nighttime low‒velocity Sub‒Auroral Ionospheric Scatter (SAIS) from decameter‒scale ionospheric density irregularities during quiet geomagnetic conditions. To establish the origin of the density irregularities responsible for low‒velocity SAIS, it is necessary to distinguish between the effects of high frequency (HF) propagation and irregularity occurrence itself on the observed backscatter distribution. We compare range, azimuth, and elevation data from the Blackstone SuperDARN radar with modeling results from ray tracing coupled with the International Reference Ionosphere assuming a uniform irregularity distribution. The observed and modeled distributions are shown to be very similar. The spatial distribution of backscattering is consistent with the requirement that HF rays propagate nearly perpendicular to the geomagnetic field lines (aspect angle ≤1°). For the first time, the irregularities responsible for low‒velocity SAIS are determined to extend between 200 and 300 km altitude, validating previous assumptions that low‒velocity SAIS is an F‒region phenomenon. We find that the limited spatial extent of this category of ionospheric backscatter within SuperDARN radars' fields‒of‒view is a consequence of HF propagation effects and the finite vertical extent of the scattering irregularities. We conclude that the density irregularities responsible for low‒velocity SAIS are widely distributed horizontally within the midlatitude ionosphere but are confined to the bottom‒side F‒region.